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uaccess: always export _copy_[from|to]_user with CONFIG_RUST

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Rust code needs to be able to access _copy_from_user and _copy_to_user
so that it can skip the check_copy_size check in cases where the length
is known at compile-time, mirroring the logic for when C code will skip
check_copy_size. To do this, we ensure that exported versions of these
methods are available when CONFIG_RUST is enabled.

Alice has verified that this patch passes the CONFIG_TEST_USER_COPY test
on x86 using the Android cuttlefish emulator.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Andrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/r/20240528-alice-mm-v7-2-78222c31b8f4@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
This commit is contained in:
Arnd Bergmann 2024-05-28 14:58:03 +00:00 committed by Miguel Ojeda
parent 1b580e7b9b
commit 1f9a8286bc
2 changed files with 36 additions and 40 deletions
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46
include/linux/uaccess.h
View File

@ -5,6 +5,7 @@
#include <linux/fault-inject-usercopy.h>
#include <linux/instrumented.h>
#include <linux/minmax.h>
#include <linux/nospec.h>
#include <linux/sched.h>
#include <linux/thread_info.h>
@ -138,13 +139,26 @@ __copy_to_user(void __user *to, const void *from, unsigned long n)
return raw_copy_to_user(to, from, n);
}
#ifdef INLINE_COPY_FROM_USER
/*
* Architectures that #define INLINE_COPY_TO_USER use this function
* directly in the normal copy_to/from_user(), the other ones go
* through an extern _copy_to/from_user(), which expands the same code
* here.
*
* Rust code always uses the extern definition.
*/
static inline __must_check unsigned long
_copy_from_user(void *to, const void __user *from, unsigned long n)
_inline_copy_from_user(void *to, const void __user *from, unsigned long n)
{
unsigned long res = n;
might_fault();
if (!should_fail_usercopy() && likely(access_ok(from, n))) {
/*
* Ensure that bad access_ok() speculation will not
* lead to nasty side effects *after* the copy is
* finished:
*/
barrier_nospec();
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);
@ -153,14 +167,11 @@ _copy_from_user(void *to, const void __user *from, unsigned long n)
memset(to + (n - res), 0, res);
return res;
}
#else
extern __must_check unsigned long
_copy_from_user(void *, const void __user *, unsigned long);
#endif
#ifdef INLINE_COPY_TO_USER
static inline __must_check unsigned long
_copy_to_user(void __user *to, const void *from, unsigned long n)
_inline_copy_to_user(void __user *to, const void *from, unsigned long n)
{
might_fault();
if (should_fail_usercopy())
@ -171,25 +182,32 @@ _copy_to_user(void __user *to, const void *from, unsigned long n)
}
return n;
}
#else
extern __must_check unsigned long
_copy_to_user(void __user *, const void *, unsigned long);
#endif
static __always_inline unsigned long __must_check
copy_from_user(void *to, const void __user *from, unsigned long n)
{
if (check_copy_size(to, n, false))
n = _copy_from_user(to, from, n);
return n;
if (!check_copy_size(to, n, false))
return n;
#ifdef INLINE_COPY_FROM_USER
return _inline_copy_from_user(to, from, n);
#else
return _copy_from_user(to, from, n);
#endif
}
static __always_inline unsigned long __must_check
copy_to_user(void __user *to, const void *from, unsigned long n)
{
if (check_copy_size(from, n, true))
n = _copy_to_user(to, from, n);
return n;
if (!check_copy_size(from, n, true))
return n;
#ifdef INLINE_COPY_TO_USER
return _inline_copy_to_user(to, from, n);
#else
return _copy_to_user(to, from, n);
#endif
}
#ifndef copy_mc_to_kernel

30
lib/usercopy.c
View File

@ -12,40 +12,18 @@
/* out-of-line parts */
#ifndef INLINE_COPY_FROM_USER
#if !defined(INLINE_COPY_FROM_USER) || defined(CONFIG_RUST)
unsigned long _copy_from_user(void *to, const void __user *from, unsigned long n)
{
unsigned long res = n;
might_fault();
if (!should_fail_usercopy() && likely(access_ok(from, n))) {
/*
* Ensure that bad access_ok() speculation will not
* lead to nasty side effects *after* the copy is
* finished:
*/
barrier_nospec();
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);
}
if (unlikely(res))
memset(to + (n - res), 0, res);
return res;
return _inline_copy_from_user(to, from, n);
}
EXPORT_SYMBOL(_copy_from_user);
#endif
#ifndef INLINE_COPY_TO_USER
#if !defined(INLINE_COPY_TO_USER) || defined(CONFIG_RUST)
unsigned long _copy_to_user(void __user *to, const void *from, unsigned long n)
{
might_fault();
if (should_fail_usercopy())
return n;
if (likely(access_ok(to, n))) {
instrument_copy_to_user(to, from, n);
n = raw_copy_to_user(to, from, n);
}
return n;
return _inline_copy_to_user(to, from, n);
}
EXPORT_SYMBOL(_copy_to_user);
#endif