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![Kirill A. Shutemov](/assets/img/avatar_default.png)
untagged_addr() removes tags/metadata from the address and brings it to the canonical form. The helper is implemented on arm64 and sparc. Both of them do untagging based on global rules. However, Linear Address Masking (LAM) on x86 introduces per-process settings for untagging. As a result, untagged_addr() is now only suitable for untagging addresses for the current proccess. The new helper untagged_addr_remote() has to be used when the address targets remote process. It requires the mmap lock for target mm to be taken. Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Tested-by: Alexander Potapenko <glider@google.com> Link: https://lore.kernel.org/all/20230312112612.31869-6-kirill.shutemov%40linux.intel.com
445 lines
14 KiB
C
445 lines
14 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_UACCESS_H__
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#define __LINUX_UACCESS_H__
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#include <linux/fault-inject-usercopy.h>
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#include <linux/instrumented.h>
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#include <linux/minmax.h>
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#include <linux/sched.h>
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#include <linux/thread_info.h>
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#include <asm/uaccess.h>
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/*
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* Architectures that support memory tagging (assigning tags to memory regions,
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* embedding these tags into addresses that point to these memory regions, and
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* checking that the memory and the pointer tags match on memory accesses)
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* redefine this macro to strip tags from pointers.
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*
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* Passing down mm_struct allows to define untagging rules on per-process
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* basis.
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*
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* It's defined as noop for architectures that don't support memory tagging.
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*/
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#ifndef untagged_addr
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#define untagged_addr(addr) (addr)
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#endif
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#ifndef untagged_addr_remote
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#define untagged_addr_remote(mm, addr) ({ \
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mmap_assert_locked(mm); \
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untagged_addr(addr); \
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})
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#endif
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/*
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* Architectures should provide two primitives (raw_copy_{to,from}_user())
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* and get rid of their private instances of copy_{to,from}_user() and
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* __copy_{to,from}_user{,_inatomic}().
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*
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* raw_copy_{to,from}_user(to, from, size) should copy up to size bytes and
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* return the amount left to copy. They should assume that access_ok() has
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* already been checked (and succeeded); they should *not* zero-pad anything.
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* No KASAN or object size checks either - those belong here.
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*
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* Both of these functions should attempt to copy size bytes starting at from
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* into the area starting at to. They must not fetch or store anything
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* outside of those areas. Return value must be between 0 (everything
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* copied successfully) and size (nothing copied).
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*
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* If raw_copy_{to,from}_user(to, from, size) returns N, size - N bytes starting
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* at to must become equal to the bytes fetched from the corresponding area
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* starting at from. All data past to + size - N must be left unmodified.
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*
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* If copying succeeds, the return value must be 0. If some data cannot be
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* fetched, it is permitted to copy less than had been fetched; the only
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* hard requirement is that not storing anything at all (i.e. returning size)
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* should happen only when nothing could be copied. In other words, you don't
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* have to squeeze as much as possible - it is allowed, but not necessary.
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*
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* For raw_copy_from_user() to always points to kernel memory and no faults
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* on store should happen. Interpretation of from is affected by set_fs().
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* For raw_copy_to_user() it's the other way round.
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*
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* Both can be inlined - it's up to architectures whether it wants to bother
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* with that. They should not be used directly; they are used to implement
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* the 6 functions (copy_{to,from}_user(), __copy_{to,from}_user_inatomic())
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* that are used instead. Out of those, __... ones are inlined. Plain
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* copy_{to,from}_user() might or might not be inlined. If you want them
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* inlined, have asm/uaccess.h define INLINE_COPY_{TO,FROM}_USER.
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*
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* NOTE: only copy_from_user() zero-pads the destination in case of short copy.
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* Neither __copy_from_user() nor __copy_from_user_inatomic() zero anything
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* at all; their callers absolutely must check the return value.
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*
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* Biarch ones should also provide raw_copy_in_user() - similar to the above,
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* but both source and destination are __user pointers (affected by set_fs()
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* as usual) and both source and destination can trigger faults.
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*/
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static __always_inline __must_check unsigned long
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__copy_from_user_inatomic(void *to, const void __user *from, unsigned long n)
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{
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unsigned long res;
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instrument_copy_from_user_before(to, from, n);
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check_object_size(to, n, false);
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res = raw_copy_from_user(to, from, n);
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instrument_copy_from_user_after(to, from, n, res);
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return res;
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}
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static __always_inline __must_check unsigned long
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__copy_from_user(void *to, const void __user *from, unsigned long n)
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{
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unsigned long res;
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might_fault();
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instrument_copy_from_user_before(to, from, n);
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if (should_fail_usercopy())
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return n;
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check_object_size(to, n, false);
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res = raw_copy_from_user(to, from, n);
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instrument_copy_from_user_after(to, from, n, res);
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return res;
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}
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/**
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* __copy_to_user_inatomic: - Copy a block of data into user space, with less checking.
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* @to: Destination address, in user space.
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* @from: Source address, in kernel space.
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* @n: Number of bytes to copy.
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*
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* Context: User context only.
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*
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* Copy data from kernel space to user space. Caller must check
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* the specified block with access_ok() before calling this function.
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* The caller should also make sure he pins the user space address
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* so that we don't result in page fault and sleep.
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*/
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static __always_inline __must_check unsigned long
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__copy_to_user_inatomic(void __user *to, const void *from, unsigned long n)
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{
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if (should_fail_usercopy())
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return n;
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instrument_copy_to_user(to, from, n);
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check_object_size(from, n, true);
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return raw_copy_to_user(to, from, n);
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}
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static __always_inline __must_check unsigned long
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__copy_to_user(void __user *to, const void *from, unsigned long n)
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{
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might_fault();
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if (should_fail_usercopy())
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return n;
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instrument_copy_to_user(to, from, n);
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check_object_size(from, n, true);
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return raw_copy_to_user(to, from, n);
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}
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#ifdef INLINE_COPY_FROM_USER
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static inline __must_check unsigned long
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_copy_from_user(void *to, const void __user *from, unsigned long n)
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{
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unsigned long res = n;
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might_fault();
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if (!should_fail_usercopy() && likely(access_ok(from, n))) {
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instrument_copy_from_user_before(to, from, n);
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res = raw_copy_from_user(to, from, n);
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instrument_copy_from_user_after(to, from, n, res);
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}
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if (unlikely(res))
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memset(to + (n - res), 0, res);
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return res;
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}
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#else
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extern __must_check unsigned long
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_copy_from_user(void *, const void __user *, unsigned long);
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#endif
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#ifdef INLINE_COPY_TO_USER
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static inline __must_check unsigned long
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_copy_to_user(void __user *to, const void *from, unsigned long n)
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{
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might_fault();
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if (should_fail_usercopy())
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return n;
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if (access_ok(to, n)) {
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instrument_copy_to_user(to, from, n);
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n = raw_copy_to_user(to, from, n);
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}
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return n;
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}
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#else
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extern __must_check unsigned long
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_copy_to_user(void __user *, const void *, unsigned long);
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#endif
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static __always_inline unsigned long __must_check
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copy_from_user(void *to, const void __user *from, unsigned long n)
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{
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if (check_copy_size(to, n, false))
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n = _copy_from_user(to, from, n);
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return n;
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}
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static __always_inline unsigned long __must_check
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copy_to_user(void __user *to, const void *from, unsigned long n)
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{
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if (check_copy_size(from, n, true))
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n = _copy_to_user(to, from, n);
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return n;
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}
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#ifndef copy_mc_to_kernel
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/*
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* Without arch opt-in this generic copy_mc_to_kernel() will not handle
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* #MC (or arch equivalent) during source read.
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*/
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static inline unsigned long __must_check
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copy_mc_to_kernel(void *dst, const void *src, size_t cnt)
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{
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memcpy(dst, src, cnt);
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return 0;
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}
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#endif
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static __always_inline void pagefault_disabled_inc(void)
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{
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current->pagefault_disabled++;
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}
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static __always_inline void pagefault_disabled_dec(void)
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{
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current->pagefault_disabled--;
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}
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/*
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* These routines enable/disable the pagefault handler. If disabled, it will
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* not take any locks and go straight to the fixup table.
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*
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* User access methods will not sleep when called from a pagefault_disabled()
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* environment.
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*/
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static inline void pagefault_disable(void)
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{
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pagefault_disabled_inc();
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/*
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* make sure to have issued the store before a pagefault
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* can hit.
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*/
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barrier();
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}
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static inline void pagefault_enable(void)
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{
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/*
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* make sure to issue those last loads/stores before enabling
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* the pagefault handler again.
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*/
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barrier();
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pagefault_disabled_dec();
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}
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/*
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* Is the pagefault handler disabled? If so, user access methods will not sleep.
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*/
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static inline bool pagefault_disabled(void)
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{
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return current->pagefault_disabled != 0;
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}
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/*
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* The pagefault handler is in general disabled by pagefault_disable() or
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* when in irq context (via in_atomic()).
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*
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* This function should only be used by the fault handlers. Other users should
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* stick to pagefault_disabled().
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* Please NEVER use preempt_disable() to disable the fault handler. With
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* !CONFIG_PREEMPT_COUNT, this is like a NOP. So the handler won't be disabled.
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* in_atomic() will report different values based on !CONFIG_PREEMPT_COUNT.
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*/
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#define faulthandler_disabled() (pagefault_disabled() || in_atomic())
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#ifndef CONFIG_ARCH_HAS_SUBPAGE_FAULTS
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/**
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* probe_subpage_writeable: probe the user range for write faults at sub-page
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* granularity (e.g. arm64 MTE)
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* @uaddr: start of address range
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* @size: size of address range
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*
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* Returns 0 on success, the number of bytes not probed on fault.
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*
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* It is expected that the caller checked for the write permission of each
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* page in the range either by put_user() or GUP. The architecture port can
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* implement a more efficient get_user() probing if the same sub-page faults
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* are triggered by either a read or a write.
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*/
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static inline size_t probe_subpage_writeable(char __user *uaddr, size_t size)
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{
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return 0;
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}
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#endif /* CONFIG_ARCH_HAS_SUBPAGE_FAULTS */
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#ifndef ARCH_HAS_NOCACHE_UACCESS
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static inline __must_check unsigned long
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__copy_from_user_inatomic_nocache(void *to, const void __user *from,
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unsigned long n)
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{
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return __copy_from_user_inatomic(to, from, n);
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}
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#endif /* ARCH_HAS_NOCACHE_UACCESS */
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extern __must_check int check_zeroed_user(const void __user *from, size_t size);
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/**
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* copy_struct_from_user: copy a struct from userspace
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* @dst: Destination address, in kernel space. This buffer must be @ksize
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* bytes long.
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* @ksize: Size of @dst struct.
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* @src: Source address, in userspace.
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* @usize: (Alleged) size of @src struct.
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*
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* Copies a struct from userspace to kernel space, in a way that guarantees
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* backwards-compatibility for struct syscall arguments (as long as future
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* struct extensions are made such that all new fields are *appended* to the
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* old struct, and zeroed-out new fields have the same meaning as the old
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* struct).
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*
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* @ksize is just sizeof(*dst), and @usize should've been passed by userspace.
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* The recommended usage is something like the following:
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*
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* SYSCALL_DEFINE2(foobar, const struct foo __user *, uarg, size_t, usize)
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* {
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* int err;
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* struct foo karg = {};
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*
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* if (usize > PAGE_SIZE)
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* return -E2BIG;
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* if (usize < FOO_SIZE_VER0)
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* return -EINVAL;
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*
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* err = copy_struct_from_user(&karg, sizeof(karg), uarg, usize);
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* if (err)
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* return err;
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*
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* // ...
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* }
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*
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* There are three cases to consider:
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* * If @usize == @ksize, then it's copied verbatim.
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* * If @usize < @ksize, then the userspace has passed an old struct to a
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* newer kernel. The rest of the trailing bytes in @dst (@ksize - @usize)
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* are to be zero-filled.
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* * If @usize > @ksize, then the userspace has passed a new struct to an
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* older kernel. The trailing bytes unknown to the kernel (@usize - @ksize)
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* are checked to ensure they are zeroed, otherwise -E2BIG is returned.
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*
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* Returns (in all cases, some data may have been copied):
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* * -E2BIG: (@usize > @ksize) and there are non-zero trailing bytes in @src.
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* * -EFAULT: access to userspace failed.
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*/
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static __always_inline __must_check int
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copy_struct_from_user(void *dst, size_t ksize, const void __user *src,
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size_t usize)
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{
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size_t size = min(ksize, usize);
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size_t rest = max(ksize, usize) - size;
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/* Double check if ksize is larger than a known object size. */
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if (WARN_ON_ONCE(ksize > __builtin_object_size(dst, 1)))
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return -E2BIG;
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/* Deal with trailing bytes. */
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if (usize < ksize) {
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memset(dst + size, 0, rest);
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} else if (usize > ksize) {
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int ret = check_zeroed_user(src + size, rest);
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if (ret <= 0)
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return ret ?: -E2BIG;
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}
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/* Copy the interoperable parts of the struct. */
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if (copy_from_user(dst, src, size))
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return -EFAULT;
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return 0;
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}
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bool copy_from_kernel_nofault_allowed(const void *unsafe_src, size_t size);
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long copy_from_kernel_nofault(void *dst, const void *src, size_t size);
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long notrace copy_to_kernel_nofault(void *dst, const void *src, size_t size);
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long copy_from_user_nofault(void *dst, const void __user *src, size_t size);
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long notrace copy_to_user_nofault(void __user *dst, const void *src,
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size_t size);
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long strncpy_from_kernel_nofault(char *dst, const void *unsafe_addr,
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long count);
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long strncpy_from_user_nofault(char *dst, const void __user *unsafe_addr,
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long count);
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long strnlen_user_nofault(const void __user *unsafe_addr, long count);
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#ifndef __get_kernel_nofault
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#define __get_kernel_nofault(dst, src, type, label) \
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do { \
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type __user *p = (type __force __user *)(src); \
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type data; \
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if (__get_user(data, p)) \
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goto label; \
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*(type *)dst = data; \
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} while (0)
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#define __put_kernel_nofault(dst, src, type, label) \
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do { \
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type __user *p = (type __force __user *)(dst); \
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type data = *(type *)src; \
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if (__put_user(data, p)) \
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goto label; \
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} while (0)
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#endif
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/**
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* get_kernel_nofault(): safely attempt to read from a location
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* @val: read into this variable
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* @ptr: address to read from
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*
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* Returns 0 on success, or -EFAULT.
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*/
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#define get_kernel_nofault(val, ptr) ({ \
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const typeof(val) *__gk_ptr = (ptr); \
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copy_from_kernel_nofault(&(val), __gk_ptr, sizeof(val));\
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})
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#ifndef user_access_begin
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#define user_access_begin(ptr,len) access_ok(ptr, len)
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#define user_access_end() do { } while (0)
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#define unsafe_op_wrap(op, err) do { if (unlikely(op)) goto err; } while (0)
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#define unsafe_get_user(x,p,e) unsafe_op_wrap(__get_user(x,p),e)
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#define unsafe_put_user(x,p,e) unsafe_op_wrap(__put_user(x,p),e)
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#define unsafe_copy_to_user(d,s,l,e) unsafe_op_wrap(__copy_to_user(d,s,l),e)
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#define unsafe_copy_from_user(d,s,l,e) unsafe_op_wrap(__copy_from_user(d,s,l),e)
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static inline unsigned long user_access_save(void) { return 0UL; }
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static inline void user_access_restore(unsigned long flags) { }
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#endif
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#ifndef user_write_access_begin
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#define user_write_access_begin user_access_begin
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#define user_write_access_end user_access_end
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#endif
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#ifndef user_read_access_begin
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#define user_read_access_begin user_access_begin
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#define user_read_access_end user_access_end
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#endif
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#ifdef CONFIG_HARDENED_USERCOPY
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void __noreturn usercopy_abort(const char *name, const char *detail,
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bool to_user, unsigned long offset,
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unsigned long len);
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#endif
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#endif /* __LINUX_UACCESS_H__ */
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