Commit 1f9a8286 authored by Arnd Bergmann's avatar Arnd Bergmann Committed by Miguel Ojeda
Browse files

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



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: default avatarArnd Bergmann <arnd@arndb.de>
Tested-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarBoqun Feng <boqun.feng@gmail.com>
Reviewed-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarAlice Ryhl <aliceryhl@google.com>
Acked-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Link: https://lore.kernel.org/r/20240528-alice-mm-v7-2-78222c31b8f4@google.com


Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent 1b580e7b

include/linux/uaccess.h

+32 −14
Original line number Diff line number Diff line
@@ -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);

	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);

	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

lib/usercopy.c

+4 −26
Original line number Diff line number Diff line
@@ -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