389 lines
12 KiB
C
389 lines
12 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 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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instrument_copy_from_user(to, from, n);
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check_object_size(to, n, false);
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return raw_copy_from_user(to, from, n);
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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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might_fault();
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if (should_fail_usercopy())
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return n;
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instrument_copy_from_user(to, from, n);
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check_object_size(to, n, false);
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return raw_copy_from_user(to, from, n);
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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(to, from, n);
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res = raw_copy_from_user(to, from, n);
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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 (likely(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 (likely(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 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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/* 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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