linux-stable/fs/kernel_read_file.c
Pasha Tatashin dabba87229 fs/kernel_read_file: allow to read files up-to ssize_t
Patch series "Allow to kexec with initramfs larger than 2G", v2.

Currently, the largest initramfs that is supported by kexec_file_load()
syscall is 2G.

This is because kernel_read_file() returns int, and is limited to INT_MAX
or 2G.

On the other hand, there are kexec based boot loaders (i.e.  u-root), that
may need to boot netboot images that might be larger than 2G.

The first patch changes the return type from int to ssize_t in
kernel_read_file* functions.

The second patch increases the maximum initramfs file size to 4G.

Tested: verified that can kexec_file_load() works with 4G initramfs
on x86_64.


This patch (of 2):

Currently, the maximum file size that is supported is 2G.  This may be too
small in some cases.  For example, kexec_file_load() system call loads
initramfs.  In some netboot cases initramfs can be rather large.

Allow to use up-to ssize_t bytes.  The callers still can limit the maximum
file size via buf_size.

Link: https://lkml.kernel.org/r/20220527025535.3953665-1-pasha.tatashin@soleen.com
Link: https://lkml.kernel.org/r/20220527025535.3953665-2-pasha.tatashin@soleen.com
Signed-off-by: Pasha Tatashin <pasha.tatashin@soleen.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Baoquan He <bhe@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Greg Thelen <gthelen@google.com>
Cc: Sasha Levin <sashal@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2022-06-16 19:58:21 -07:00

189 lines
4.4 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
#include <linux/fs.h>
#include <linux/fs_struct.h>
#include <linux/kernel_read_file.h>
#include <linux/security.h>
#include <linux/vmalloc.h>
/**
* kernel_read_file() - read file contents into a kernel buffer
*
* @file file to read from
* @offset where to start reading from (see below).
* @buf pointer to a "void *" buffer for reading into (if
* *@buf is NULL, a buffer will be allocated, and
* @buf_size will be ignored)
* @buf_size size of buf, if already allocated. If @buf not
* allocated, this is the largest size to allocate.
* @file_size if non-NULL, the full size of @file will be
* written here.
* @id the kernel_read_file_id identifying the type of
* file contents being read (for LSMs to examine)
*
* @offset must be 0 unless both @buf and @file_size are non-NULL
* (i.e. the caller must be expecting to read partial file contents
* via an already-allocated @buf, in at most @buf_size chunks, and
* will be able to determine when the entire file was read by
* checking @file_size). This isn't a recommended way to read a
* file, though, since it is possible that the contents might
* change between calls to kernel_read_file().
*
* Returns number of bytes read (no single read will be bigger
* than SSIZE_MAX), or negative on error.
*
*/
ssize_t kernel_read_file(struct file *file, loff_t offset, void **buf,
size_t buf_size, size_t *file_size,
enum kernel_read_file_id id)
{
loff_t i_size, pos;
ssize_t copied;
void *allocated = NULL;
bool whole_file;
int ret;
if (offset != 0 && (!*buf || !file_size))
return -EINVAL;
if (!S_ISREG(file_inode(file)->i_mode))
return -EINVAL;
ret = deny_write_access(file);
if (ret)
return ret;
i_size = i_size_read(file_inode(file));
if (i_size <= 0) {
ret = -EINVAL;
goto out;
}
/* The file is too big for sane activities. */
if (i_size > SSIZE_MAX) {
ret = -EFBIG;
goto out;
}
/* The entire file cannot be read in one buffer. */
if (!file_size && offset == 0 && i_size > buf_size) {
ret = -EFBIG;
goto out;
}
whole_file = (offset == 0 && i_size <= buf_size);
ret = security_kernel_read_file(file, id, whole_file);
if (ret)
goto out;
if (file_size)
*file_size = i_size;
if (!*buf)
*buf = allocated = vmalloc(i_size);
if (!*buf) {
ret = -ENOMEM;
goto out;
}
pos = offset;
copied = 0;
while (copied < buf_size) {
ssize_t bytes;
size_t wanted = min_t(size_t, buf_size - copied,
i_size - pos);
bytes = kernel_read(file, *buf + copied, wanted, &pos);
if (bytes < 0) {
ret = bytes;
goto out_free;
}
if (bytes == 0)
break;
copied += bytes;
}
if (whole_file) {
if (pos != i_size) {
ret = -EIO;
goto out_free;
}
ret = security_kernel_post_read_file(file, *buf, i_size, id);
}
out_free:
if (ret < 0) {
if (allocated) {
vfree(*buf);
*buf = NULL;
}
}
out:
allow_write_access(file);
return ret == 0 ? copied : ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file);
ssize_t kernel_read_file_from_path(const char *path, loff_t offset, void **buf,
size_t buf_size, size_t *file_size,
enum kernel_read_file_id id)
{
struct file *file;
ssize_t ret;
if (!path || !*path)
return -EINVAL;
file = filp_open(path, O_RDONLY, 0);
if (IS_ERR(file))
return PTR_ERR(file);
ret = kernel_read_file(file, offset, buf, buf_size, file_size, id);
fput(file);
return ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file_from_path);
ssize_t kernel_read_file_from_path_initns(const char *path, loff_t offset,
void **buf, size_t buf_size,
size_t *file_size,
enum kernel_read_file_id id)
{
struct file *file;
struct path root;
ssize_t ret;
if (!path || !*path)
return -EINVAL;
task_lock(&init_task);
get_fs_root(init_task.fs, &root);
task_unlock(&init_task);
file = file_open_root(&root, path, O_RDONLY, 0);
path_put(&root);
if (IS_ERR(file))
return PTR_ERR(file);
ret = kernel_read_file(file, offset, buf, buf_size, file_size, id);
fput(file);
return ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file_from_path_initns);
ssize_t kernel_read_file_from_fd(int fd, loff_t offset, void **buf,
size_t buf_size, size_t *file_size,
enum kernel_read_file_id id)
{
struct fd f = fdget(fd);
ssize_t ret = -EBADF;
if (!f.file || !(f.file->f_mode & FMODE_READ))
goto out;
ret = kernel_read_file(f.file, offset, buf, buf_size, file_size, id);
out:
fdput(f);
return ret;
}
EXPORT_SYMBOL_GPL(kernel_read_file_from_fd);