linux-stable/lib/iov_iter.c
Linus Torvalds 307e14c039 46 fs/cifs (smb3 client) changesets, 37 in fs/cifs and 9 for related helper functions and cleanup outside from Dave Howells and Willy
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Merge tag '6.3-rc-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6

Pull cifs client updates from Steve French:
 "The largest subset of this is from David Howells et al: making the
  cifs/smb3 driver pass iov_iters down to the lowest layers, directly to
  the network transport rather than passing lists of pages around,
  helping multiple areas:

   - Pin user pages, thereby fixing the race between concurrent DIO read
     and fork, where the pages containing the DIO read buffer may end up
     belonging to the child process and not the parent - with the result
     that the parent might not see the retrieved data.

   - cifs shouldn't take refs on pages extracted from non-user-backed
     iterators (eg. KVEC). With these changes, cifs will apply the
     appropriate cleanup.

   - Making it easier to transition to using folios in cifs rather than
     pages by dealing with them through BVEC and XARRAY iterators.

   - Allowing cifs to use the new splice function

  The remainder are:

   - fixes for stable, including various fixes for uninitialized memory,
     wrong length field causing mount issue to very old servers,
     important directory lease fixes and reconnect fixes

   - cleanups (unused code removal, change one element array usage, and
     a change form strtobool to kstrtobool, and Kconfig cleanups)

   - SMBDIRECT (RDMA) fixes including iov_iter integration and UAF fixes

   - reconnect fixes

   - multichannel fixes, including improving channel allocation (to
     least used channel)

   - remove the last use of lock_page_killable by moving to
     folio_lock_killable"

* tag '6.3-rc-smb3-client-fixes' of git://git.samba.org/sfrench/cifs-2.6: (46 commits)
  update internal module version number for cifs.ko
  cifs: update ip_addr for ses only for primary chan setup
  cifs: use tcon allocation functions even for dummy tcon
  cifs: use the least loaded channel for sending requests
  cifs: DIO to/from KVEC-type iterators should now work
  cifs: Remove unused code
  cifs: Build the RDMA SGE list directly from an iterator
  cifs: Change the I/O paths to use an iterator rather than a page list
  cifs: Add a function to read into an iter from a socket
  cifs: Add some helper functions
  cifs: Add a function to Hash the contents of an iterator
  cifs: Add a function to build an RDMA SGE list from an iterator
  netfs: Add a function to extract an iterator into a scatterlist
  netfs: Add a function to extract a UBUF or IOVEC into a BVEC iterator
  cifs: Implement splice_read to pass down ITER_BVEC not ITER_PIPE
  splice: Export filemap/direct_splice_read()
  iov_iter: Add a function to extract a page list from an iterator
  iov_iter: Define flags to qualify page extraction.
  splice: Add a func to do a splice from an O_DIRECT file without ITER_PIPE
  splice: Add a func to do a splice from a buffered file without ITER_PIPE
  ...
2023-02-22 17:12:44 -08:00

2187 lines
54 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#include <crypto/hash.h>
#include <linux/export.h>
#include <linux/bvec.h>
#include <linux/fault-inject-usercopy.h>
#include <linux/uio.h>
#include <linux/pagemap.h>
#include <linux/highmem.h>
#include <linux/slab.h>
#include <linux/vmalloc.h>
#include <linux/splice.h>
#include <linux/compat.h>
#include <net/checksum.h>
#include <linux/scatterlist.h>
#include <linux/instrumented.h>
#define PIPE_PARANOIA /* for now */
/* covers ubuf and kbuf alike */
#define iterate_buf(i, n, base, len, off, __p, STEP) { \
size_t __maybe_unused off = 0; \
len = n; \
base = __p + i->iov_offset; \
len -= (STEP); \
i->iov_offset += len; \
n = len; \
}
/* covers iovec and kvec alike */
#define iterate_iovec(i, n, base, len, off, __p, STEP) { \
size_t off = 0; \
size_t skip = i->iov_offset; \
do { \
len = min(n, __p->iov_len - skip); \
if (likely(len)) { \
base = __p->iov_base + skip; \
len -= (STEP); \
off += len; \
skip += len; \
n -= len; \
if (skip < __p->iov_len) \
break; \
} \
__p++; \
skip = 0; \
} while (n); \
i->iov_offset = skip; \
n = off; \
}
#define iterate_bvec(i, n, base, len, off, p, STEP) { \
size_t off = 0; \
unsigned skip = i->iov_offset; \
while (n) { \
unsigned offset = p->bv_offset + skip; \
unsigned left; \
void *kaddr = kmap_local_page(p->bv_page + \
offset / PAGE_SIZE); \
base = kaddr + offset % PAGE_SIZE; \
len = min(min(n, (size_t)(p->bv_len - skip)), \
(size_t)(PAGE_SIZE - offset % PAGE_SIZE)); \
left = (STEP); \
kunmap_local(kaddr); \
len -= left; \
off += len; \
skip += len; \
if (skip == p->bv_len) { \
skip = 0; \
p++; \
} \
n -= len; \
if (left) \
break; \
} \
i->iov_offset = skip; \
n = off; \
}
#define iterate_xarray(i, n, base, len, __off, STEP) { \
__label__ __out; \
size_t __off = 0; \
struct folio *folio; \
loff_t start = i->xarray_start + i->iov_offset; \
pgoff_t index = start / PAGE_SIZE; \
XA_STATE(xas, i->xarray, index); \
\
len = PAGE_SIZE - offset_in_page(start); \
rcu_read_lock(); \
xas_for_each(&xas, folio, ULONG_MAX) { \
unsigned left; \
size_t offset; \
if (xas_retry(&xas, folio)) \
continue; \
if (WARN_ON(xa_is_value(folio))) \
break; \
if (WARN_ON(folio_test_hugetlb(folio))) \
break; \
offset = offset_in_folio(folio, start + __off); \
while (offset < folio_size(folio)) { \
base = kmap_local_folio(folio, offset); \
len = min(n, len); \
left = (STEP); \
kunmap_local(base); \
len -= left; \
__off += len; \
n -= len; \
if (left || n == 0) \
goto __out; \
offset += len; \
len = PAGE_SIZE; \
} \
} \
__out: \
rcu_read_unlock(); \
i->iov_offset += __off; \
n = __off; \
}
#define __iterate_and_advance(i, n, base, len, off, I, K) { \
if (unlikely(i->count < n)) \
n = i->count; \
if (likely(n)) { \
if (likely(iter_is_ubuf(i))) { \
void __user *base; \
size_t len; \
iterate_buf(i, n, base, len, off, \
i->ubuf, (I)) \
} else if (likely(iter_is_iovec(i))) { \
const struct iovec *iov = i->iov; \
void __user *base; \
size_t len; \
iterate_iovec(i, n, base, len, off, \
iov, (I)) \
i->nr_segs -= iov - i->iov; \
i->iov = iov; \
} else if (iov_iter_is_bvec(i)) { \
const struct bio_vec *bvec = i->bvec; \
void *base; \
size_t len; \
iterate_bvec(i, n, base, len, off, \
bvec, (K)) \
i->nr_segs -= bvec - i->bvec; \
i->bvec = bvec; \
} else if (iov_iter_is_kvec(i)) { \
const struct kvec *kvec = i->kvec; \
void *base; \
size_t len; \
iterate_iovec(i, n, base, len, off, \
kvec, (K)) \
i->nr_segs -= kvec - i->kvec; \
i->kvec = kvec; \
} else if (iov_iter_is_xarray(i)) { \
void *base; \
size_t len; \
iterate_xarray(i, n, base, len, off, \
(K)) \
} \
i->count -= n; \
} \
}
#define iterate_and_advance(i, n, base, len, off, I, K) \
__iterate_and_advance(i, n, base, len, off, I, ((void)(K),0))
static int copyout(void __user *to, const void *from, size_t n)
{
if (should_fail_usercopy())
return n;
if (access_ok(to, n)) {
instrument_copy_to_user(to, from, n);
n = raw_copy_to_user(to, from, n);
}
return n;
}
static int copyin(void *to, const void __user *from, size_t n)
{
size_t res = n;
if (should_fail_usercopy())
return n;
if (access_ok(from, n)) {
instrument_copy_from_user_before(to, from, n);
res = raw_copy_from_user(to, from, n);
instrument_copy_from_user_after(to, from, n, res);
}
return res;
}
#ifdef PIPE_PARANOIA
static bool sanity(const struct iov_iter *i)
{
struct pipe_inode_info *pipe = i->pipe;
unsigned int p_head = pipe->head;
unsigned int p_tail = pipe->tail;
unsigned int p_occupancy = pipe_occupancy(p_head, p_tail);
unsigned int i_head = i->head;
unsigned int idx;
if (i->last_offset) {
struct pipe_buffer *p;
if (unlikely(p_occupancy == 0))
goto Bad; // pipe must be non-empty
if (unlikely(i_head != p_head - 1))
goto Bad; // must be at the last buffer...
p = pipe_buf(pipe, i_head);
if (unlikely(p->offset + p->len != abs(i->last_offset)))
goto Bad; // ... at the end of segment
} else {
if (i_head != p_head)
goto Bad; // must be right after the last buffer
}
return true;
Bad:
printk(KERN_ERR "idx = %d, offset = %d\n", i_head, i->last_offset);
printk(KERN_ERR "head = %d, tail = %d, buffers = %d\n",
p_head, p_tail, pipe->ring_size);
for (idx = 0; idx < pipe->ring_size; idx++)
printk(KERN_ERR "[%p %p %d %d]\n",
pipe->bufs[idx].ops,
pipe->bufs[idx].page,
pipe->bufs[idx].offset,
pipe->bufs[idx].len);
WARN_ON(1);
return false;
}
#else
#define sanity(i) true
#endif
static struct page *push_anon(struct pipe_inode_info *pipe, unsigned size)
{
struct page *page = alloc_page(GFP_USER);
if (page) {
struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++);
*buf = (struct pipe_buffer) {
.ops = &default_pipe_buf_ops,
.page = page,
.offset = 0,
.len = size
};
}
return page;
}
static void push_page(struct pipe_inode_info *pipe, struct page *page,
unsigned int offset, unsigned int size)
{
struct pipe_buffer *buf = pipe_buf(pipe, pipe->head++);
*buf = (struct pipe_buffer) {
.ops = &page_cache_pipe_buf_ops,
.page = page,
.offset = offset,
.len = size
};
get_page(page);
}
static inline int last_offset(const struct pipe_buffer *buf)
{
if (buf->ops == &default_pipe_buf_ops)
return buf->len; // buf->offset is 0 for those
else
return -(buf->offset + buf->len);
}
static struct page *append_pipe(struct iov_iter *i, size_t size,
unsigned int *off)
{
struct pipe_inode_info *pipe = i->pipe;
int offset = i->last_offset;
struct pipe_buffer *buf;
struct page *page;
if (offset > 0 && offset < PAGE_SIZE) {
// some space in the last buffer; add to it
buf = pipe_buf(pipe, pipe->head - 1);
size = min_t(size_t, size, PAGE_SIZE - offset);
buf->len += size;
i->last_offset += size;
i->count -= size;
*off = offset;
return buf->page;
}
// OK, we need a new buffer
*off = 0;
size = min_t(size_t, size, PAGE_SIZE);
if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
return NULL;
page = push_anon(pipe, size);
if (!page)
return NULL;
i->head = pipe->head - 1;
i->last_offset = size;
i->count -= size;
return page;
}
static size_t copy_page_to_iter_pipe(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
struct pipe_inode_info *pipe = i->pipe;
unsigned int head = pipe->head;
if (unlikely(bytes > i->count))
bytes = i->count;
if (unlikely(!bytes))
return 0;
if (!sanity(i))
return 0;
if (offset && i->last_offset == -offset) { // could we merge it?
struct pipe_buffer *buf = pipe_buf(pipe, head - 1);
if (buf->page == page) {
buf->len += bytes;
i->last_offset -= bytes;
i->count -= bytes;
return bytes;
}
}
if (pipe_full(pipe->head, pipe->tail, pipe->max_usage))
return 0;
push_page(pipe, page, offset, bytes);
i->last_offset = -(offset + bytes);
i->head = head;
i->count -= bytes;
return bytes;
}
/*
* fault_in_iov_iter_readable - fault in iov iterator for reading
* @i: iterator
* @size: maximum length
*
* Fault in one or more iovecs of the given iov_iter, to a maximum length of
* @size. For each iovec, fault in each page that constitutes the iovec.
*
* Returns the number of bytes not faulted in (like copy_to_user() and
* copy_from_user()).
*
* Always returns 0 for non-userspace iterators.
*/
size_t fault_in_iov_iter_readable(const struct iov_iter *i, size_t size)
{
if (iter_is_ubuf(i)) {
size_t n = min(size, iov_iter_count(i));
n -= fault_in_readable(i->ubuf + i->iov_offset, n);
return size - n;
} else if (iter_is_iovec(i)) {
size_t count = min(size, iov_iter_count(i));
const struct iovec *p;
size_t skip;
size -= count;
for (p = i->iov, skip = i->iov_offset; count; p++, skip = 0) {
size_t len = min(count, p->iov_len - skip);
size_t ret;
if (unlikely(!len))
continue;
ret = fault_in_readable(p->iov_base + skip, len);
count -= len - ret;
if (ret)
break;
}
return count + size;
}
return 0;
}
EXPORT_SYMBOL(fault_in_iov_iter_readable);
/*
* fault_in_iov_iter_writeable - fault in iov iterator for writing
* @i: iterator
* @size: maximum length
*
* Faults in the iterator using get_user_pages(), i.e., without triggering
* hardware page faults. This is primarily useful when we already know that
* some or all of the pages in @i aren't in memory.
*
* Returns the number of bytes not faulted in, like copy_to_user() and
* copy_from_user().
*
* Always returns 0 for non-user-space iterators.
*/
size_t fault_in_iov_iter_writeable(const struct iov_iter *i, size_t size)
{
if (iter_is_ubuf(i)) {
size_t n = min(size, iov_iter_count(i));
n -= fault_in_safe_writeable(i->ubuf + i->iov_offset, n);
return size - n;
} else if (iter_is_iovec(i)) {
size_t count = min(size, iov_iter_count(i));
const struct iovec *p;
size_t skip;
size -= count;
for (p = i->iov, skip = i->iov_offset; count; p++, skip = 0) {
size_t len = min(count, p->iov_len - skip);
size_t ret;
if (unlikely(!len))
continue;
ret = fault_in_safe_writeable(p->iov_base + skip, len);
count -= len - ret;
if (ret)
break;
}
return count + size;
}
return 0;
}
EXPORT_SYMBOL(fault_in_iov_iter_writeable);
void iov_iter_init(struct iov_iter *i, unsigned int direction,
const struct iovec *iov, unsigned long nr_segs,
size_t count)
{
WARN_ON(direction & ~(READ | WRITE));
*i = (struct iov_iter) {
.iter_type = ITER_IOVEC,
.nofault = false,
.user_backed = true,
.data_source = direction,
.iov = iov,
.nr_segs = nr_segs,
.iov_offset = 0,
.count = count
};
}
EXPORT_SYMBOL(iov_iter_init);
// returns the offset in partial buffer (if any)
static inline unsigned int pipe_npages(const struct iov_iter *i, int *npages)
{
struct pipe_inode_info *pipe = i->pipe;
int used = pipe->head - pipe->tail;
int off = i->last_offset;
*npages = max((int)pipe->max_usage - used, 0);
if (off > 0 && off < PAGE_SIZE) { // anon and not full
(*npages)++;
return off;
}
return 0;
}
static size_t copy_pipe_to_iter(const void *addr, size_t bytes,
struct iov_iter *i)
{
unsigned int off, chunk;
if (unlikely(bytes > i->count))
bytes = i->count;
if (unlikely(!bytes))
return 0;
if (!sanity(i))
return 0;
for (size_t n = bytes; n; n -= chunk) {
struct page *page = append_pipe(i, n, &off);
chunk = min_t(size_t, n, PAGE_SIZE - off);
if (!page)
return bytes - n;
memcpy_to_page(page, off, addr, chunk);
addr += chunk;
}
return bytes;
}
static __wsum csum_and_memcpy(void *to, const void *from, size_t len,
__wsum sum, size_t off)
{
__wsum next = csum_partial_copy_nocheck(from, to, len);
return csum_block_add(sum, next, off);
}
static size_t csum_and_copy_to_pipe_iter(const void *addr, size_t bytes,
struct iov_iter *i, __wsum *sump)
{
__wsum sum = *sump;
size_t off = 0;
unsigned int chunk, r;
if (unlikely(bytes > i->count))
bytes = i->count;
if (unlikely(!bytes))
return 0;
if (!sanity(i))
return 0;
while (bytes) {
struct page *page = append_pipe(i, bytes, &r);
char *p;
if (!page)
break;
chunk = min_t(size_t, bytes, PAGE_SIZE - r);
p = kmap_local_page(page);
sum = csum_and_memcpy(p + r, addr + off, chunk, sum, off);
kunmap_local(p);
off += chunk;
bytes -= chunk;
}
*sump = sum;
return off;
}
size_t _copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(i->data_source))
return 0;
if (unlikely(iov_iter_is_pipe(i)))
return copy_pipe_to_iter(addr, bytes, i);
if (user_backed_iter(i))
might_fault();
iterate_and_advance(i, bytes, base, len, off,
copyout(base, addr + off, len),
memcpy(base, addr + off, len)
)
return bytes;
}
EXPORT_SYMBOL(_copy_to_iter);
#ifdef CONFIG_ARCH_HAS_COPY_MC
static int copyout_mc(void __user *to, const void *from, size_t n)
{
if (access_ok(to, n)) {
instrument_copy_to_user(to, from, n);
n = copy_mc_to_user((__force void *) to, from, n);
}
return n;
}
static size_t copy_mc_pipe_to_iter(const void *addr, size_t bytes,
struct iov_iter *i)
{
size_t xfer = 0;
unsigned int off, chunk;
if (unlikely(bytes > i->count))
bytes = i->count;
if (unlikely(!bytes))
return 0;
if (!sanity(i))
return 0;
while (bytes) {
struct page *page = append_pipe(i, bytes, &off);
unsigned long rem;
char *p;
if (!page)
break;
chunk = min_t(size_t, bytes, PAGE_SIZE - off);
p = kmap_local_page(page);
rem = copy_mc_to_kernel(p + off, addr + xfer, chunk);
chunk -= rem;
kunmap_local(p);
xfer += chunk;
bytes -= chunk;
if (rem) {
iov_iter_revert(i, rem);
break;
}
}
return xfer;
}
/**
* _copy_mc_to_iter - copy to iter with source memory error exception handling
* @addr: source kernel address
* @bytes: total transfer length
* @i: destination iterator
*
* The pmem driver deploys this for the dax operation
* (dax_copy_to_iter()) for dax reads (bypass page-cache and the
* block-layer). Upon #MC read(2) aborts and returns EIO or the bytes
* successfully copied.
*
* The main differences between this and typical _copy_to_iter().
*
* * Typical tail/residue handling after a fault retries the copy
* byte-by-byte until the fault happens again. Re-triggering machine
* checks is potentially fatal so the implementation uses source
* alignment and poison alignment assumptions to avoid re-triggering
* hardware exceptions.
*
* * ITER_KVEC, ITER_PIPE, and ITER_BVEC can return short copies.
* Compare to copy_to_iter() where only ITER_IOVEC attempts might return
* a short copy.
*
* Return: number of bytes copied (may be %0)
*/
size_t _copy_mc_to_iter(const void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(i->data_source))
return 0;
if (unlikely(iov_iter_is_pipe(i)))
return copy_mc_pipe_to_iter(addr, bytes, i);
if (user_backed_iter(i))
might_fault();
__iterate_and_advance(i, bytes, base, len, off,
copyout_mc(base, addr + off, len),
copy_mc_to_kernel(base, addr + off, len)
)
return bytes;
}
EXPORT_SYMBOL_GPL(_copy_mc_to_iter);
#endif /* CONFIG_ARCH_HAS_COPY_MC */
size_t _copy_from_iter(void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(!i->data_source))
return 0;
if (user_backed_iter(i))
might_fault();
iterate_and_advance(i, bytes, base, len, off,
copyin(addr + off, base, len),
memcpy(addr + off, base, len)
)
return bytes;
}
EXPORT_SYMBOL(_copy_from_iter);
size_t _copy_from_iter_nocache(void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(!i->data_source))
return 0;
iterate_and_advance(i, bytes, base, len, off,
__copy_from_user_inatomic_nocache(addr + off, base, len),
memcpy(addr + off, base, len)
)
return bytes;
}
EXPORT_SYMBOL(_copy_from_iter_nocache);
#ifdef CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE
/**
* _copy_from_iter_flushcache - write destination through cpu cache
* @addr: destination kernel address
* @bytes: total transfer length
* @i: source iterator
*
* The pmem driver arranges for filesystem-dax to use this facility via
* dax_copy_from_iter() for ensuring that writes to persistent memory
* are flushed through the CPU cache. It is differentiated from
* _copy_from_iter_nocache() in that guarantees all data is flushed for
* all iterator types. The _copy_from_iter_nocache() only attempts to
* bypass the cache for the ITER_IOVEC case, and on some archs may use
* instructions that strand dirty-data in the cache.
*
* Return: number of bytes copied (may be %0)
*/
size_t _copy_from_iter_flushcache(void *addr, size_t bytes, struct iov_iter *i)
{
if (WARN_ON_ONCE(!i->data_source))
return 0;
iterate_and_advance(i, bytes, base, len, off,
__copy_from_user_flushcache(addr + off, base, len),
memcpy_flushcache(addr + off, base, len)
)
return bytes;
}
EXPORT_SYMBOL_GPL(_copy_from_iter_flushcache);
#endif
static inline bool page_copy_sane(struct page *page, size_t offset, size_t n)
{
struct page *head;
size_t v = n + offset;
/*
* The general case needs to access the page order in order
* to compute the page size.
* However, we mostly deal with order-0 pages and thus can
* avoid a possible cache line miss for requests that fit all
* page orders.
*/
if (n <= v && v <= PAGE_SIZE)
return true;
head = compound_head(page);
v += (page - head) << PAGE_SHIFT;
if (WARN_ON(n > v || v > page_size(head)))
return false;
return true;
}
size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t res = 0;
if (!page_copy_sane(page, offset, bytes))
return 0;
if (WARN_ON_ONCE(i->data_source))
return 0;
if (unlikely(iov_iter_is_pipe(i)))
return copy_page_to_iter_pipe(page, offset, bytes, i);
page += offset / PAGE_SIZE; // first subpage
offset %= PAGE_SIZE;
while (1) {
void *kaddr = kmap_local_page(page);
size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
n = _copy_to_iter(kaddr + offset, n, i);
kunmap_local(kaddr);
res += n;
bytes -= n;
if (!bytes || !n)
break;
offset += n;
if (offset == PAGE_SIZE) {
page++;
offset = 0;
}
}
return res;
}
EXPORT_SYMBOL(copy_page_to_iter);
size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,
struct iov_iter *i)
{
size_t res = 0;
if (!page_copy_sane(page, offset, bytes))
return 0;
page += offset / PAGE_SIZE; // first subpage
offset %= PAGE_SIZE;
while (1) {
void *kaddr = kmap_local_page(page);
size_t n = min(bytes, (size_t)PAGE_SIZE - offset);
n = _copy_from_iter(kaddr + offset, n, i);
kunmap_local(kaddr);
res += n;
bytes -= n;
if (!bytes || !n)
break;
offset += n;
if (offset == PAGE_SIZE) {
page++;
offset = 0;
}
}
return res;
}
EXPORT_SYMBOL(copy_page_from_iter);
static size_t pipe_zero(size_t bytes, struct iov_iter *i)
{
unsigned int chunk, off;
if (unlikely(bytes > i->count))
bytes = i->count;
if (unlikely(!bytes))
return 0;
if (!sanity(i))
return 0;
for (size_t n = bytes; n; n -= chunk) {
struct page *page = append_pipe(i, n, &off);
char *p;
if (!page)
return bytes - n;
chunk = min_t(size_t, n, PAGE_SIZE - off);
p = kmap_local_page(page);
memset(p + off, 0, chunk);
kunmap_local(p);
}
return bytes;
}
size_t iov_iter_zero(size_t bytes, struct iov_iter *i)
{
if (unlikely(iov_iter_is_pipe(i)))
return pipe_zero(bytes, i);
iterate_and_advance(i, bytes, base, len, count,
clear_user(base, len),
memset(base, 0, len)
)
return bytes;
}
EXPORT_SYMBOL(iov_iter_zero);
size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes,
struct iov_iter *i)
{
char *kaddr = kmap_atomic(page), *p = kaddr + offset;
if (!page_copy_sane(page, offset, bytes)) {
kunmap_atomic(kaddr);
return 0;
}
if (WARN_ON_ONCE(!i->data_source)) {
kunmap_atomic(kaddr);
return 0;
}
iterate_and_advance(i, bytes, base, len, off,
copyin(p + off, base, len),
memcpy(p + off, base, len)
)
kunmap_atomic(kaddr);
return bytes;
}
EXPORT_SYMBOL(copy_page_from_iter_atomic);
static void pipe_advance(struct iov_iter *i, size_t size)
{
struct pipe_inode_info *pipe = i->pipe;
int off = i->last_offset;
if (!off && !size) {
pipe_discard_from(pipe, i->start_head); // discard everything
return;
}
i->count -= size;
while (1) {
struct pipe_buffer *buf = pipe_buf(pipe, i->head);
if (off) /* make it relative to the beginning of buffer */
size += abs(off) - buf->offset;
if (size <= buf->len) {
buf->len = size;
i->last_offset = last_offset(buf);
break;
}
size -= buf->len;
i->head++;
off = 0;
}
pipe_discard_from(pipe, i->head + 1); // discard everything past this one
}
static void iov_iter_bvec_advance(struct iov_iter *i, size_t size)
{
const struct bio_vec *bvec, *end;
if (!i->count)
return;
i->count -= size;
size += i->iov_offset;
for (bvec = i->bvec, end = bvec + i->nr_segs; bvec < end; bvec++) {
if (likely(size < bvec->bv_len))
break;
size -= bvec->bv_len;
}
i->iov_offset = size;
i->nr_segs -= bvec - i->bvec;
i->bvec = bvec;
}
static void iov_iter_iovec_advance(struct iov_iter *i, size_t size)
{
const struct iovec *iov, *end;
if (!i->count)
return;
i->count -= size;
size += i->iov_offset; // from beginning of current segment
for (iov = i->iov, end = iov + i->nr_segs; iov < end; iov++) {
if (likely(size < iov->iov_len))
break;
size -= iov->iov_len;
}
i->iov_offset = size;
i->nr_segs -= iov - i->iov;
i->iov = iov;
}
void iov_iter_advance(struct iov_iter *i, size_t size)
{
if (unlikely(i->count < size))
size = i->count;
if (likely(iter_is_ubuf(i)) || unlikely(iov_iter_is_xarray(i))) {
i->iov_offset += size;
i->count -= size;
} else if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i))) {
/* iovec and kvec have identical layouts */
iov_iter_iovec_advance(i, size);
} else if (iov_iter_is_bvec(i)) {
iov_iter_bvec_advance(i, size);
} else if (iov_iter_is_pipe(i)) {
pipe_advance(i, size);
} else if (iov_iter_is_discard(i)) {
i->count -= size;
}
}
EXPORT_SYMBOL(iov_iter_advance);
void iov_iter_revert(struct iov_iter *i, size_t unroll)
{
if (!unroll)
return;
if (WARN_ON(unroll > MAX_RW_COUNT))
return;
i->count += unroll;
if (unlikely(iov_iter_is_pipe(i))) {
struct pipe_inode_info *pipe = i->pipe;
unsigned int head = pipe->head;
while (head > i->start_head) {
struct pipe_buffer *b = pipe_buf(pipe, --head);
if (unroll < b->len) {
b->len -= unroll;
i->last_offset = last_offset(b);
i->head = head;
return;
}
unroll -= b->len;
pipe_buf_release(pipe, b);
pipe->head--;
}
i->last_offset = 0;
i->head = head;
return;
}
if (unlikely(iov_iter_is_discard(i)))
return;
if (unroll <= i->iov_offset) {
i->iov_offset -= unroll;
return;
}
unroll -= i->iov_offset;
if (iov_iter_is_xarray(i) || iter_is_ubuf(i)) {
BUG(); /* We should never go beyond the start of the specified
* range since we might then be straying into pages that
* aren't pinned.
*/
} else if (iov_iter_is_bvec(i)) {
const struct bio_vec *bvec = i->bvec;
while (1) {
size_t n = (--bvec)->bv_len;
i->nr_segs++;
if (unroll <= n) {
i->bvec = bvec;
i->iov_offset = n - unroll;
return;
}
unroll -= n;
}
} else { /* same logics for iovec and kvec */
const struct iovec *iov = i->iov;
while (1) {
size_t n = (--iov)->iov_len;
i->nr_segs++;
if (unroll <= n) {
i->iov = iov;
i->iov_offset = n - unroll;
return;
}
unroll -= n;
}
}
}
EXPORT_SYMBOL(iov_iter_revert);
/*
* Return the count of just the current iov_iter segment.
*/
size_t iov_iter_single_seg_count(const struct iov_iter *i)
{
if (i->nr_segs > 1) {
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return min(i->count, i->iov->iov_len - i->iov_offset);
if (iov_iter_is_bvec(i))
return min(i->count, i->bvec->bv_len - i->iov_offset);
}
return i->count;
}
EXPORT_SYMBOL(iov_iter_single_seg_count);
void iov_iter_kvec(struct iov_iter *i, unsigned int direction,
const struct kvec *kvec, unsigned long nr_segs,
size_t count)
{
WARN_ON(direction & ~(READ | WRITE));
*i = (struct iov_iter){
.iter_type = ITER_KVEC,
.data_source = direction,
.kvec = kvec,
.nr_segs = nr_segs,
.iov_offset = 0,
.count = count
};
}
EXPORT_SYMBOL(iov_iter_kvec);
void iov_iter_bvec(struct iov_iter *i, unsigned int direction,
const struct bio_vec *bvec, unsigned long nr_segs,
size_t count)
{
WARN_ON(direction & ~(READ | WRITE));
*i = (struct iov_iter){
.iter_type = ITER_BVEC,
.data_source = direction,
.bvec = bvec,
.nr_segs = nr_segs,
.iov_offset = 0,
.count = count
};
}
EXPORT_SYMBOL(iov_iter_bvec);
void iov_iter_pipe(struct iov_iter *i, unsigned int direction,
struct pipe_inode_info *pipe,
size_t count)
{
BUG_ON(direction != READ);
WARN_ON(pipe_full(pipe->head, pipe->tail, pipe->ring_size));
*i = (struct iov_iter){
.iter_type = ITER_PIPE,
.data_source = false,
.pipe = pipe,
.head = pipe->head,
.start_head = pipe->head,
.last_offset = 0,
.count = count
};
}
EXPORT_SYMBOL(iov_iter_pipe);
/**
* iov_iter_xarray - Initialise an I/O iterator to use the pages in an xarray
* @i: The iterator to initialise.
* @direction: The direction of the transfer.
* @xarray: The xarray to access.
* @start: The start file position.
* @count: The size of the I/O buffer in bytes.
*
* Set up an I/O iterator to either draw data out of the pages attached to an
* inode or to inject data into those pages. The pages *must* be prevented
* from evaporation, either by taking a ref on them or locking them by the
* caller.
*/
void iov_iter_xarray(struct iov_iter *i, unsigned int direction,
struct xarray *xarray, loff_t start, size_t count)
{
BUG_ON(direction & ~1);
*i = (struct iov_iter) {
.iter_type = ITER_XARRAY,
.data_source = direction,
.xarray = xarray,
.xarray_start = start,
.count = count,
.iov_offset = 0
};
}
EXPORT_SYMBOL(iov_iter_xarray);
/**
* iov_iter_discard - Initialise an I/O iterator that discards data
* @i: The iterator to initialise.
* @direction: The direction of the transfer.
* @count: The size of the I/O buffer in bytes.
*
* Set up an I/O iterator that just discards everything that's written to it.
* It's only available as a READ iterator.
*/
void iov_iter_discard(struct iov_iter *i, unsigned int direction, size_t count)
{
BUG_ON(direction != READ);
*i = (struct iov_iter){
.iter_type = ITER_DISCARD,
.data_source = false,
.count = count,
.iov_offset = 0
};
}
EXPORT_SYMBOL(iov_iter_discard);
static bool iov_iter_aligned_iovec(const struct iov_iter *i, unsigned addr_mask,
unsigned len_mask)
{
size_t size = i->count;
size_t skip = i->iov_offset;
unsigned k;
for (k = 0; k < i->nr_segs; k++, skip = 0) {
size_t len = i->iov[k].iov_len - skip;
if (len > size)
len = size;
if (len & len_mask)
return false;
if ((unsigned long)(i->iov[k].iov_base + skip) & addr_mask)
return false;
size -= len;
if (!size)
break;
}
return true;
}
static bool iov_iter_aligned_bvec(const struct iov_iter *i, unsigned addr_mask,
unsigned len_mask)
{
size_t size = i->count;
unsigned skip = i->iov_offset;
unsigned k;
for (k = 0; k < i->nr_segs; k++, skip = 0) {
size_t len = i->bvec[k].bv_len - skip;
if (len > size)
len = size;
if (len & len_mask)
return false;
if ((unsigned long)(i->bvec[k].bv_offset + skip) & addr_mask)
return false;
size -= len;
if (!size)
break;
}
return true;
}
/**
* iov_iter_is_aligned() - Check if the addresses and lengths of each segments
* are aligned to the parameters.
*
* @i: &struct iov_iter to restore
* @addr_mask: bit mask to check against the iov element's addresses
* @len_mask: bit mask to check against the iov element's lengths
*
* Return: false if any addresses or lengths intersect with the provided masks
*/
bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask,
unsigned len_mask)
{
if (likely(iter_is_ubuf(i))) {
if (i->count & len_mask)
return false;
if ((unsigned long)(i->ubuf + i->iov_offset) & addr_mask)
return false;
return true;
}
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return iov_iter_aligned_iovec(i, addr_mask, len_mask);
if (iov_iter_is_bvec(i))
return iov_iter_aligned_bvec(i, addr_mask, len_mask);
if (iov_iter_is_pipe(i)) {
size_t size = i->count;
if (size & len_mask)
return false;
if (size && i->last_offset > 0) {
if (i->last_offset & addr_mask)
return false;
}
return true;
}
if (iov_iter_is_xarray(i)) {
if (i->count & len_mask)
return false;
if ((i->xarray_start + i->iov_offset) & addr_mask)
return false;
}
return true;
}
EXPORT_SYMBOL_GPL(iov_iter_is_aligned);
static unsigned long iov_iter_alignment_iovec(const struct iov_iter *i)
{
unsigned long res = 0;
size_t size = i->count;
size_t skip = i->iov_offset;
unsigned k;
for (k = 0; k < i->nr_segs; k++, skip = 0) {
size_t len = i->iov[k].iov_len - skip;
if (len) {
res |= (unsigned long)i->iov[k].iov_base + skip;
if (len > size)
len = size;
res |= len;
size -= len;
if (!size)
break;
}
}
return res;
}
static unsigned long iov_iter_alignment_bvec(const struct iov_iter *i)
{
unsigned res = 0;
size_t size = i->count;
unsigned skip = i->iov_offset;
unsigned k;
for (k = 0; k < i->nr_segs; k++, skip = 0) {
size_t len = i->bvec[k].bv_len - skip;
res |= (unsigned long)i->bvec[k].bv_offset + skip;
if (len > size)
len = size;
res |= len;
size -= len;
if (!size)
break;
}
return res;
}
unsigned long iov_iter_alignment(const struct iov_iter *i)
{
if (likely(iter_is_ubuf(i))) {
size_t size = i->count;
if (size)
return ((unsigned long)i->ubuf + i->iov_offset) | size;
return 0;
}
/* iovec and kvec have identical layouts */
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return iov_iter_alignment_iovec(i);
if (iov_iter_is_bvec(i))
return iov_iter_alignment_bvec(i);
if (iov_iter_is_pipe(i)) {
size_t size = i->count;
if (size && i->last_offset > 0)
return size | i->last_offset;
return size;
}
if (iov_iter_is_xarray(i))
return (i->xarray_start + i->iov_offset) | i->count;
return 0;
}
EXPORT_SYMBOL(iov_iter_alignment);
unsigned long iov_iter_gap_alignment(const struct iov_iter *i)
{
unsigned long res = 0;
unsigned long v = 0;
size_t size = i->count;
unsigned k;
if (iter_is_ubuf(i))
return 0;
if (WARN_ON(!iter_is_iovec(i)))
return ~0U;
for (k = 0; k < i->nr_segs; k++) {
if (i->iov[k].iov_len) {
unsigned long base = (unsigned long)i->iov[k].iov_base;
if (v) // if not the first one
res |= base | v; // this start | previous end
v = base + i->iov[k].iov_len;
if (size <= i->iov[k].iov_len)
break;
size -= i->iov[k].iov_len;
}
}
return res;
}
EXPORT_SYMBOL(iov_iter_gap_alignment);
static int want_pages_array(struct page ***res, size_t size,
size_t start, unsigned int maxpages)
{
unsigned int count = DIV_ROUND_UP(size + start, PAGE_SIZE);
if (count > maxpages)
count = maxpages;
WARN_ON(!count); // caller should've prevented that
if (!*res) {
*res = kvmalloc_array(count, sizeof(struct page *), GFP_KERNEL);
if (!*res)
return 0;
}
return count;
}
static ssize_t pipe_get_pages(struct iov_iter *i,
struct page ***pages, size_t maxsize, unsigned maxpages,
size_t *start)
{
unsigned int npages, count, off, chunk;
struct page **p;
size_t left;
if (!sanity(i))
return -EFAULT;
*start = off = pipe_npages(i, &npages);
if (!npages)
return -EFAULT;
count = want_pages_array(pages, maxsize, off, min(npages, maxpages));
if (!count)
return -ENOMEM;
p = *pages;
for (npages = 0, left = maxsize ; npages < count; npages++, left -= chunk) {
struct page *page = append_pipe(i, left, &off);
if (!page)
break;
chunk = min_t(size_t, left, PAGE_SIZE - off);
get_page(*p++ = page);
}
if (!npages)
return -EFAULT;
return maxsize - left;
}
static ssize_t iter_xarray_populate_pages(struct page **pages, struct xarray *xa,
pgoff_t index, unsigned int nr_pages)
{
XA_STATE(xas, xa, index);
struct page *page;
unsigned int ret = 0;
rcu_read_lock();
for (page = xas_load(&xas); page; page = xas_next(&xas)) {
if (xas_retry(&xas, page))
continue;
/* Has the page moved or been split? */
if (unlikely(page != xas_reload(&xas))) {
xas_reset(&xas);
continue;
}
pages[ret] = find_subpage(page, xas.xa_index);
get_page(pages[ret]);
if (++ret == nr_pages)
break;
}
rcu_read_unlock();
return ret;
}
static ssize_t iter_xarray_get_pages(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned maxpages, size_t *_start_offset)
{
unsigned nr, offset, count;
pgoff_t index;
loff_t pos;
pos = i->xarray_start + i->iov_offset;
index = pos >> PAGE_SHIFT;
offset = pos & ~PAGE_MASK;
*_start_offset = offset;
count = want_pages_array(pages, maxsize, offset, maxpages);
if (!count)
return -ENOMEM;
nr = iter_xarray_populate_pages(*pages, i->xarray, index, count);
if (nr == 0)
return 0;
maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
i->iov_offset += maxsize;
i->count -= maxsize;
return maxsize;
}
/* must be done on non-empty ITER_UBUF or ITER_IOVEC one */
static unsigned long first_iovec_segment(const struct iov_iter *i, size_t *size)
{
size_t skip;
long k;
if (iter_is_ubuf(i))
return (unsigned long)i->ubuf + i->iov_offset;
for (k = 0, skip = i->iov_offset; k < i->nr_segs; k++, skip = 0) {
size_t len = i->iov[k].iov_len - skip;
if (unlikely(!len))
continue;
if (*size > len)
*size = len;
return (unsigned long)i->iov[k].iov_base + skip;
}
BUG(); // if it had been empty, we wouldn't get called
}
/* must be done on non-empty ITER_BVEC one */
static struct page *first_bvec_segment(const struct iov_iter *i,
size_t *size, size_t *start)
{
struct page *page;
size_t skip = i->iov_offset, len;
len = i->bvec->bv_len - skip;
if (*size > len)
*size = len;
skip += i->bvec->bv_offset;
page = i->bvec->bv_page + skip / PAGE_SIZE;
*start = skip % PAGE_SIZE;
return page;
}
static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned int maxpages, size_t *start,
iov_iter_extraction_t extraction_flags)
{
unsigned int n, gup_flags = 0;
if (maxsize > i->count)
maxsize = i->count;
if (!maxsize)
return 0;
if (maxsize > MAX_RW_COUNT)
maxsize = MAX_RW_COUNT;
if (extraction_flags & ITER_ALLOW_P2PDMA)
gup_flags |= FOLL_PCI_P2PDMA;
if (likely(user_backed_iter(i))) {
unsigned long addr;
int res;
if (iov_iter_rw(i) != WRITE)
gup_flags |= FOLL_WRITE;
if (i->nofault)
gup_flags |= FOLL_NOFAULT;
addr = first_iovec_segment(i, &maxsize);
*start = addr % PAGE_SIZE;
addr &= PAGE_MASK;
n = want_pages_array(pages, maxsize, *start, maxpages);
if (!n)
return -ENOMEM;
res = get_user_pages_fast(addr, n, gup_flags, *pages);
if (unlikely(res <= 0))
return res;
maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - *start);
iov_iter_advance(i, maxsize);
return maxsize;
}
if (iov_iter_is_bvec(i)) {
struct page **p;
struct page *page;
page = first_bvec_segment(i, &maxsize, start);
n = want_pages_array(pages, maxsize, *start, maxpages);
if (!n)
return -ENOMEM;
p = *pages;
for (int k = 0; k < n; k++)
get_page(p[k] = page + k);
maxsize = min_t(size_t, maxsize, n * PAGE_SIZE - *start);
i->count -= maxsize;
i->iov_offset += maxsize;
if (i->iov_offset == i->bvec->bv_len) {
i->iov_offset = 0;
i->bvec++;
i->nr_segs--;
}
return maxsize;
}
if (iov_iter_is_pipe(i))
return pipe_get_pages(i, pages, maxsize, maxpages, start);
if (iov_iter_is_xarray(i))
return iter_xarray_get_pages(i, pages, maxsize, maxpages, start);
return -EFAULT;
}
ssize_t iov_iter_get_pages(struct iov_iter *i,
struct page **pages, size_t maxsize, unsigned maxpages,
size_t *start, iov_iter_extraction_t extraction_flags)
{
if (!maxpages)
return 0;
BUG_ON(!pages);
return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages,
start, extraction_flags);
}
EXPORT_SYMBOL_GPL(iov_iter_get_pages);
ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages,
size_t maxsize, unsigned maxpages, size_t *start)
{
return iov_iter_get_pages(i, pages, maxsize, maxpages, start, 0);
}
EXPORT_SYMBOL(iov_iter_get_pages2);
ssize_t iov_iter_get_pages_alloc(struct iov_iter *i,
struct page ***pages, size_t maxsize,
size_t *start, iov_iter_extraction_t extraction_flags)
{
ssize_t len;
*pages = NULL;
len = __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start,
extraction_flags);
if (len <= 0) {
kvfree(*pages);
*pages = NULL;
}
return len;
}
EXPORT_SYMBOL_GPL(iov_iter_get_pages_alloc);
ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i,
struct page ***pages, size_t maxsize, size_t *start)
{
return iov_iter_get_pages_alloc(i, pages, maxsize, start, 0);
}
EXPORT_SYMBOL(iov_iter_get_pages_alloc2);
size_t csum_and_copy_from_iter(void *addr, size_t bytes, __wsum *csum,
struct iov_iter *i)
{
__wsum sum, next;
sum = *csum;
if (WARN_ON_ONCE(!i->data_source))
return 0;
iterate_and_advance(i, bytes, base, len, off, ({
next = csum_and_copy_from_user(base, addr + off, len);
sum = csum_block_add(sum, next, off);
next ? 0 : len;
}), ({
sum = csum_and_memcpy(addr + off, base, len, sum, off);
})
)
*csum = sum;
return bytes;
}
EXPORT_SYMBOL(csum_and_copy_from_iter);
size_t csum_and_copy_to_iter(const void *addr, size_t bytes, void *_csstate,
struct iov_iter *i)
{
struct csum_state *csstate = _csstate;
__wsum sum, next;
if (WARN_ON_ONCE(i->data_source))
return 0;
if (unlikely(iov_iter_is_discard(i))) {
// can't use csum_memcpy() for that one - data is not copied
csstate->csum = csum_block_add(csstate->csum,
csum_partial(addr, bytes, 0),
csstate->off);
csstate->off += bytes;
return bytes;
}
sum = csum_shift(csstate->csum, csstate->off);
if (unlikely(iov_iter_is_pipe(i)))
bytes = csum_and_copy_to_pipe_iter(addr, bytes, i, &sum);
else iterate_and_advance(i, bytes, base, len, off, ({
next = csum_and_copy_to_user(addr + off, base, len);
sum = csum_block_add(sum, next, off);
next ? 0 : len;
}), ({
sum = csum_and_memcpy(base, addr + off, len, sum, off);
})
)
csstate->csum = csum_shift(sum, csstate->off);
csstate->off += bytes;
return bytes;
}
EXPORT_SYMBOL(csum_and_copy_to_iter);
size_t hash_and_copy_to_iter(const void *addr, size_t bytes, void *hashp,
struct iov_iter *i)
{
#ifdef CONFIG_CRYPTO_HASH
struct ahash_request *hash = hashp;
struct scatterlist sg;
size_t copied;
copied = copy_to_iter(addr, bytes, i);
sg_init_one(&sg, addr, copied);
ahash_request_set_crypt(hash, &sg, NULL, copied);
crypto_ahash_update(hash);
return copied;
#else
return 0;
#endif
}
EXPORT_SYMBOL(hash_and_copy_to_iter);
static int iov_npages(const struct iov_iter *i, int maxpages)
{
size_t skip = i->iov_offset, size = i->count;
const struct iovec *p;
int npages = 0;
for (p = i->iov; size; skip = 0, p++) {
unsigned offs = offset_in_page(p->iov_base + skip);
size_t len = min(p->iov_len - skip, size);
if (len) {
size -= len;
npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
if (unlikely(npages > maxpages))
return maxpages;
}
}
return npages;
}
static int bvec_npages(const struct iov_iter *i, int maxpages)
{
size_t skip = i->iov_offset, size = i->count;
const struct bio_vec *p;
int npages = 0;
for (p = i->bvec; size; skip = 0, p++) {
unsigned offs = (p->bv_offset + skip) % PAGE_SIZE;
size_t len = min(p->bv_len - skip, size);
size -= len;
npages += DIV_ROUND_UP(offs + len, PAGE_SIZE);
if (unlikely(npages > maxpages))
return maxpages;
}
return npages;
}
int iov_iter_npages(const struct iov_iter *i, int maxpages)
{
if (unlikely(!i->count))
return 0;
if (likely(iter_is_ubuf(i))) {
unsigned offs = offset_in_page(i->ubuf + i->iov_offset);
int npages = DIV_ROUND_UP(offs + i->count, PAGE_SIZE);
return min(npages, maxpages);
}
/* iovec and kvec have identical layouts */
if (likely(iter_is_iovec(i) || iov_iter_is_kvec(i)))
return iov_npages(i, maxpages);
if (iov_iter_is_bvec(i))
return bvec_npages(i, maxpages);
if (iov_iter_is_pipe(i)) {
int npages;
if (!sanity(i))
return 0;
pipe_npages(i, &npages);
return min(npages, maxpages);
}
if (iov_iter_is_xarray(i)) {
unsigned offset = (i->xarray_start + i->iov_offset) % PAGE_SIZE;
int npages = DIV_ROUND_UP(offset + i->count, PAGE_SIZE);
return min(npages, maxpages);
}
return 0;
}
EXPORT_SYMBOL(iov_iter_npages);
const void *dup_iter(struct iov_iter *new, struct iov_iter *old, gfp_t flags)
{
*new = *old;
if (unlikely(iov_iter_is_pipe(new))) {
WARN_ON(1);
return NULL;
}
if (iov_iter_is_bvec(new))
return new->bvec = kmemdup(new->bvec,
new->nr_segs * sizeof(struct bio_vec),
flags);
else if (iov_iter_is_kvec(new) || iter_is_iovec(new))
/* iovec and kvec have identical layout */
return new->iov = kmemdup(new->iov,
new->nr_segs * sizeof(struct iovec),
flags);
return NULL;
}
EXPORT_SYMBOL(dup_iter);
static int copy_compat_iovec_from_user(struct iovec *iov,
const struct iovec __user *uvec, unsigned long nr_segs)
{
const struct compat_iovec __user *uiov =
(const struct compat_iovec __user *)uvec;
int ret = -EFAULT, i;
if (!user_access_begin(uiov, nr_segs * sizeof(*uiov)))
return -EFAULT;
for (i = 0; i < nr_segs; i++) {
compat_uptr_t buf;
compat_ssize_t len;
unsafe_get_user(len, &uiov[i].iov_len, uaccess_end);
unsafe_get_user(buf, &uiov[i].iov_base, uaccess_end);
/* check for compat_size_t not fitting in compat_ssize_t .. */
if (len < 0) {
ret = -EINVAL;
goto uaccess_end;
}
iov[i].iov_base = compat_ptr(buf);
iov[i].iov_len = len;
}
ret = 0;
uaccess_end:
user_access_end();
return ret;
}
static int copy_iovec_from_user(struct iovec *iov,
const struct iovec __user *uvec, unsigned long nr_segs)
{
unsigned long seg;
if (copy_from_user(iov, uvec, nr_segs * sizeof(*uvec)))
return -EFAULT;
for (seg = 0; seg < nr_segs; seg++) {
if ((ssize_t)iov[seg].iov_len < 0)
return -EINVAL;
}
return 0;
}
struct iovec *iovec_from_user(const struct iovec __user *uvec,
unsigned long nr_segs, unsigned long fast_segs,
struct iovec *fast_iov, bool compat)
{
struct iovec *iov = fast_iov;
int ret;
/*
* SuS says "The readv() function *may* fail if the iovcnt argument was
* less than or equal to 0, or greater than {IOV_MAX}. Linux has
* traditionally returned zero for zero segments, so...
*/
if (nr_segs == 0)
return iov;
if (nr_segs > UIO_MAXIOV)
return ERR_PTR(-EINVAL);
if (nr_segs > fast_segs) {
iov = kmalloc_array(nr_segs, sizeof(struct iovec), GFP_KERNEL);
if (!iov)
return ERR_PTR(-ENOMEM);
}
if (compat)
ret = copy_compat_iovec_from_user(iov, uvec, nr_segs);
else
ret = copy_iovec_from_user(iov, uvec, nr_segs);
if (ret) {
if (iov != fast_iov)
kfree(iov);
return ERR_PTR(ret);
}
return iov;
}
ssize_t __import_iovec(int type, const struct iovec __user *uvec,
unsigned nr_segs, unsigned fast_segs, struct iovec **iovp,
struct iov_iter *i, bool compat)
{
ssize_t total_len = 0;
unsigned long seg;
struct iovec *iov;
iov = iovec_from_user(uvec, nr_segs, fast_segs, *iovp, compat);
if (IS_ERR(iov)) {
*iovp = NULL;
return PTR_ERR(iov);
}
/*
* According to the Single Unix Specification we should return EINVAL if
* an element length is < 0 when cast to ssize_t or if the total length
* would overflow the ssize_t return value of the system call.
*
* Linux caps all read/write calls to MAX_RW_COUNT, and avoids the
* overflow case.
*/
for (seg = 0; seg < nr_segs; seg++) {
ssize_t len = (ssize_t)iov[seg].iov_len;
if (!access_ok(iov[seg].iov_base, len)) {
if (iov != *iovp)
kfree(iov);
*iovp = NULL;
return -EFAULT;
}
if (len > MAX_RW_COUNT - total_len) {
len = MAX_RW_COUNT - total_len;
iov[seg].iov_len = len;
}
total_len += len;
}
iov_iter_init(i, type, iov, nr_segs, total_len);
if (iov == *iovp)
*iovp = NULL;
else
*iovp = iov;
return total_len;
}
/**
* import_iovec() - Copy an array of &struct iovec from userspace
* into the kernel, check that it is valid, and initialize a new
* &struct iov_iter iterator to access it.
*
* @type: One of %READ or %WRITE.
* @uvec: Pointer to the userspace array.
* @nr_segs: Number of elements in userspace array.
* @fast_segs: Number of elements in @iov.
* @iovp: (input and output parameter) Pointer to pointer to (usually small
* on-stack) kernel array.
* @i: Pointer to iterator that will be initialized on success.
*
* If the array pointed to by *@iov is large enough to hold all @nr_segs,
* then this function places %NULL in *@iov on return. Otherwise, a new
* array will be allocated and the result placed in *@iov. This means that
* the caller may call kfree() on *@iov regardless of whether the small
* on-stack array was used or not (and regardless of whether this function
* returns an error or not).
*
* Return: Negative error code on error, bytes imported on success
*/
ssize_t import_iovec(int type, const struct iovec __user *uvec,
unsigned nr_segs, unsigned fast_segs,
struct iovec **iovp, struct iov_iter *i)
{
return __import_iovec(type, uvec, nr_segs, fast_segs, iovp, i,
in_compat_syscall());
}
EXPORT_SYMBOL(import_iovec);
int import_single_range(int rw, void __user *buf, size_t len,
struct iovec *iov, struct iov_iter *i)
{
if (len > MAX_RW_COUNT)
len = MAX_RW_COUNT;
if (unlikely(!access_ok(buf, len)))
return -EFAULT;
iov->iov_base = buf;
iov->iov_len = len;
iov_iter_init(i, rw, iov, 1, len);
return 0;
}
EXPORT_SYMBOL(import_single_range);
int import_ubuf(int rw, void __user *buf, size_t len, struct iov_iter *i)
{
if (len > MAX_RW_COUNT)
len = MAX_RW_COUNT;
if (unlikely(!access_ok(buf, len)))
return -EFAULT;
iov_iter_ubuf(i, rw, buf, len);
return 0;
}
/**
* iov_iter_restore() - Restore a &struct iov_iter to the same state as when
* iov_iter_save_state() was called.
*
* @i: &struct iov_iter to restore
* @state: state to restore from
*
* Used after iov_iter_save_state() to bring restore @i, if operations may
* have advanced it.
*
* Note: only works on ITER_IOVEC, ITER_BVEC, and ITER_KVEC
*/
void iov_iter_restore(struct iov_iter *i, struct iov_iter_state *state)
{
if (WARN_ON_ONCE(!iov_iter_is_bvec(i) && !iter_is_iovec(i) &&
!iter_is_ubuf(i)) && !iov_iter_is_kvec(i))
return;
i->iov_offset = state->iov_offset;
i->count = state->count;
if (iter_is_ubuf(i))
return;
/*
* For the *vec iters, nr_segs + iov is constant - if we increment
* the vec, then we also decrement the nr_segs count. Hence we don't
* need to track both of these, just one is enough and we can deduct
* the other from that. ITER_KVEC and ITER_IOVEC are the same struct
* size, so we can just increment the iov pointer as they are unionzed.
* ITER_BVEC _may_ be the same size on some archs, but on others it is
* not. Be safe and handle it separately.
*/
BUILD_BUG_ON(sizeof(struct iovec) != sizeof(struct kvec));
if (iov_iter_is_bvec(i))
i->bvec -= state->nr_segs - i->nr_segs;
else
i->iov -= state->nr_segs - i->nr_segs;
i->nr_segs = state->nr_segs;
}
/*
* Extract a list of contiguous pages from an ITER_XARRAY iterator. This does not
* get references on the pages, nor does it get a pin on them.
*/
static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
struct page *page, **p;
unsigned int nr = 0, offset;
loff_t pos = i->xarray_start + i->iov_offset;
pgoff_t index = pos >> PAGE_SHIFT;
XA_STATE(xas, i->xarray, index);
offset = pos & ~PAGE_MASK;
*offset0 = offset;
maxpages = want_pages_array(pages, maxsize, offset, maxpages);
if (!maxpages)
return -ENOMEM;
p = *pages;
rcu_read_lock();
for (page = xas_load(&xas); page; page = xas_next(&xas)) {
if (xas_retry(&xas, page))
continue;
/* Has the page moved or been split? */
if (unlikely(page != xas_reload(&xas))) {
xas_reset(&xas);
continue;
}
p[nr++] = find_subpage(page, xas.xa_index);
if (nr == maxpages)
break;
}
rcu_read_unlock();
maxsize = min_t(size_t, nr * PAGE_SIZE - offset, maxsize);
iov_iter_advance(i, maxsize);
return maxsize;
}
/*
* Extract a list of contiguous pages from an ITER_BVEC iterator. This does
* not get references on the pages, nor does it get a pin on them.
*/
static ssize_t iov_iter_extract_bvec_pages(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
struct page **p, *page;
size_t skip = i->iov_offset, offset;
int k;
for (;;) {
if (i->nr_segs == 0)
return 0;
maxsize = min(maxsize, i->bvec->bv_len - skip);
if (maxsize)
break;
i->iov_offset = 0;
i->nr_segs--;
i->bvec++;
skip = 0;
}
skip += i->bvec->bv_offset;
page = i->bvec->bv_page + skip / PAGE_SIZE;
offset = skip % PAGE_SIZE;
*offset0 = offset;
maxpages = want_pages_array(pages, maxsize, offset, maxpages);
if (!maxpages)
return -ENOMEM;
p = *pages;
for (k = 0; k < maxpages; k++)
p[k] = page + k;
maxsize = min_t(size_t, maxsize, maxpages * PAGE_SIZE - offset);
iov_iter_advance(i, maxsize);
return maxsize;
}
/*
* Extract a list of virtually contiguous pages from an ITER_KVEC iterator.
* This does not get references on the pages, nor does it get a pin on them.
*/
static ssize_t iov_iter_extract_kvec_pages(struct iov_iter *i,
struct page ***pages, size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
struct page **p, *page;
const void *kaddr;
size_t skip = i->iov_offset, offset, len;
int k;
for (;;) {
if (i->nr_segs == 0)
return 0;
maxsize = min(maxsize, i->kvec->iov_len - skip);
if (maxsize)
break;
i->iov_offset = 0;
i->nr_segs--;
i->kvec++;
skip = 0;
}
kaddr = i->kvec->iov_base + skip;
offset = (unsigned long)kaddr & ~PAGE_MASK;
*offset0 = offset;
maxpages = want_pages_array(pages, maxsize, offset, maxpages);
if (!maxpages)
return -ENOMEM;
p = *pages;
kaddr -= offset;
len = offset + maxsize;
for (k = 0; k < maxpages; k++) {
size_t seg = min_t(size_t, len, PAGE_SIZE);
if (is_vmalloc_or_module_addr(kaddr))
page = vmalloc_to_page(kaddr);
else
page = virt_to_page(kaddr);
p[k] = page;
len -= seg;
kaddr += PAGE_SIZE;
}
maxsize = min_t(size_t, maxsize, maxpages * PAGE_SIZE - offset);
iov_iter_advance(i, maxsize);
return maxsize;
}
/*
* Extract a list of contiguous pages from a user iterator and get a pin on
* each of them. This should only be used if the iterator is user-backed
* (IOBUF/UBUF).
*
* It does not get refs on the pages, but the pages must be unpinned by the
* caller once the transfer is complete.
*
* This is safe to be used where background IO/DMA *is* going to be modifying
* the buffer; using a pin rather than a ref makes forces fork() to give the
* child a copy of the page.
*/
static ssize_t iov_iter_extract_user_pages(struct iov_iter *i,
struct page ***pages,
size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
unsigned long addr;
unsigned int gup_flags = 0;
size_t offset;
int res;
if (i->data_source == ITER_DEST)
gup_flags |= FOLL_WRITE;
if (extraction_flags & ITER_ALLOW_P2PDMA)
gup_flags |= FOLL_PCI_P2PDMA;
if (i->nofault)
gup_flags |= FOLL_NOFAULT;
addr = first_iovec_segment(i, &maxsize);
*offset0 = offset = addr % PAGE_SIZE;
addr &= PAGE_MASK;
maxpages = want_pages_array(pages, maxsize, offset, maxpages);
if (!maxpages)
return -ENOMEM;
res = pin_user_pages_fast(addr, maxpages, gup_flags, *pages);
if (unlikely(res <= 0))
return res;
maxsize = min_t(size_t, maxsize, res * PAGE_SIZE - offset);
iov_iter_advance(i, maxsize);
return maxsize;
}
/**
* iov_iter_extract_pages - Extract a list of contiguous pages from an iterator
* @i: The iterator to extract from
* @pages: Where to return the list of pages
* @maxsize: The maximum amount of iterator to extract
* @maxpages: The maximum size of the list of pages
* @extraction_flags: Flags to qualify request
* @offset0: Where to return the starting offset into (*@pages)[0]
*
* Extract a list of contiguous pages from the current point of the iterator,
* advancing the iterator. The maximum number of pages and the maximum amount
* of page contents can be set.
*
* If *@pages is NULL, a page list will be allocated to the required size and
* *@pages will be set to its base. If *@pages is not NULL, it will be assumed
* that the caller allocated a page list at least @maxpages in size and this
* will be filled in.
*
* @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-peer DMA
* be allowed on the pages extracted.
*
* The iov_iter_extract_will_pin() function can be used to query how cleanup
* should be performed.
*
* Extra refs or pins on the pages may be obtained as follows:
*
* (*) If the iterator is user-backed (ITER_IOVEC/ITER_UBUF), pins will be
* added to the pages, but refs will not be taken.
* iov_iter_extract_will_pin() will return true.
*
* (*) If the iterator is ITER_KVEC, ITER_BVEC or ITER_XARRAY, the pages are
* merely listed; no extra refs or pins are obtained.
* iov_iter_extract_will_pin() will return 0.
*
* Note also:
*
* (*) Use with ITER_DISCARD is not supported as that has no content.
*
* On success, the function sets *@pages to the new pagelist, if allocated, and
* sets *offset0 to the offset into the first page.
*
* It may also return -ENOMEM and -EFAULT.
*/
ssize_t iov_iter_extract_pages(struct iov_iter *i,
struct page ***pages,
size_t maxsize,
unsigned int maxpages,
iov_iter_extraction_t extraction_flags,
size_t *offset0)
{
maxsize = min_t(size_t, min_t(size_t, maxsize, i->count), MAX_RW_COUNT);
if (!maxsize)
return 0;
if (likely(user_backed_iter(i)))
return iov_iter_extract_user_pages(i, pages, maxsize,
maxpages, extraction_flags,
offset0);
if (iov_iter_is_kvec(i))
return iov_iter_extract_kvec_pages(i, pages, maxsize,
maxpages, extraction_flags,
offset0);
if (iov_iter_is_bvec(i))
return iov_iter_extract_bvec_pages(i, pages, maxsize,
maxpages, extraction_flags,
offset0);
if (iov_iter_is_xarray(i))
return iov_iter_extract_xarray_pages(i, pages, maxsize,
maxpages, extraction_flags,
offset0);
return -EFAULT;
}
EXPORT_SYMBOL_GPL(iov_iter_extract_pages);