Commit 75cf0290 authored by Alexander Potapenko's avatar Alexander Potapenko Committed by Andrew Morton
Browse files

instrumented.h: add KMSAN support 

To avoid false positives, KMSAN needs to unpoison the data copied from the
userspace.  To detect infoleaks - check the memory buffer passed to
copy_to_user().

Link: https://lkml.kernel.org/r/20220915150417.722975-19-glider@google.com


Signed-off-by: default avatarAlexander Potapenko <glider@google.com>
Reviewed-by: default avatarMarco Elver <elver@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 3c206509

include/linux/instrumented.h

+13 −5
Original line number Diff line number Diff line
@@ -2,7 +2,7 @@ 


/*

 * This header provides generic wrappers for memory access instrumentation that

 * the compiler cannot emit for: KASAN, KCSAN.

 * the compiler cannot emit for: KASAN, KCSAN, KMSAN.

 */

#ifndef _LINUX_INSTRUMENTED_H

#define _LINUX_INSTRUMENTED_H
@@ -10,6 +10,7 @@ 
#include <linux/compiler.h>

#include <linux/kasan-checks.h>

#include <linux/kcsan-checks.h>

#include <linux/kmsan-checks.h>

#include <linux/types.h>



/**
@@ -117,6 +118,7 @@ instrument_copy_to_user(void __user *to, const void *from, unsigned long n) 
{

	kasan_check_read(from, n);

	kcsan_check_read(from, n);

	kmsan_copy_to_user(to, from, n, 0);

}



/**
@@ -151,6 +153,7 @@ static __always_inline void 
instrument_copy_from_user_after(const void *to, const void __user *from,

				unsigned long n, unsigned long left)

{

	kmsan_unpoison_memory(to, n - left);

}



/**
@@ -164,8 +167,12 @@ instrument_copy_from_user_after(const void *to, const void __user *from, 
 */

#define instrument_get_user(to)				\

({							\

	u64 __tmp = (u64)(to);				\

	kmsan_unpoison_memory(&__tmp, sizeof(__tmp));	\

	to = __tmp;					\

})





/**

 * instrument_put_user() - add instrumentation to put_user()-like macros

 *
@@ -179,6 +186,7 @@ instrument_copy_from_user_after(const void *to, const void __user *from, 
 */

#define instrument_put_user(from, ptr, size)			\

({								\

	kmsan_copy_to_user(ptr, &from, sizeof(from), 0);	\

})



#endif /* _LINUX_INSTRUMENTED_H */

include/linux/kmsan-checks.h

+19 −0
Original line number Diff line number Diff line
@@ -46,6 +46,21 @@ void kmsan_unpoison_memory(const void *address, size_t size); 
 */

void kmsan_check_memory(const void *address, size_t size);



/**

 * kmsan_copy_to_user() - Notify KMSAN about a data transfer to userspace.

 * @to:      destination address in the userspace.

 * @from:    source address in the kernel.

 * @to_copy: number of bytes to copy.

 * @left:    number of bytes not copied.

 *

 * If this is a real userspace data transfer, KMSAN checks the bytes that were

 * actually copied to ensure there was no information leak. If @to belongs to

 * the kernel space (which is possible for compat syscalls), KMSAN just copies

 * the metadata.

 */

void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,

			size_t left);



#else



static inline void kmsan_poison_memory(const void *address, size_t size,
@@ -58,6 +73,10 @@ static inline void kmsan_unpoison_memory(const void *address, size_t size) 
static inline void kmsan_check_memory(const void *address, size_t size)

{

}

static inline void kmsan_copy_to_user(void __user *to, const void *from,

				      size_t to_copy, size_t left)

{

}



#endif

mm/kmsan/hooks.c

+38 −0
Original line number Diff line number Diff line
@@ -205,6 +205,44 @@ void kmsan_iounmap_page_range(unsigned long start, unsigned long end) 
	kmsan_leave_runtime();

}



void kmsan_copy_to_user(void __user *to, const void *from, size_t to_copy,

			size_t left)

{

	unsigned long ua_flags;



	if (!kmsan_enabled || kmsan_in_runtime())

		return;

	/*

	 * At this point we've copied the memory already. It's hard to check it

	 * before copying, as the size of actually copied buffer is unknown.

	 */



	/* copy_to_user() may copy zero bytes. No need to check. */

	if (!to_copy)

		return;

	/* Or maybe copy_to_user() failed to copy anything. */

	if (to_copy <= left)

		return;



	ua_flags = user_access_save();

	if ((u64)to < TASK_SIZE) {

		/* This is a user memory access, check it. */

		kmsan_internal_check_memory((void *)from, to_copy - left, to,

					    REASON_COPY_TO_USER);

	} else {

		/* Otherwise this is a kernel memory access. This happens when a

		 * compat syscall passes an argument allocated on the kernel

		 * stack to a real syscall.

		 * Don't check anything, just copy the shadow of the copied

		 * bytes.

		 */

		kmsan_internal_memmove_metadata((void *)to, (void *)from,

						to_copy - left);

	}

	user_access_restore(ua_flags);

}

EXPORT_SYMBOL(kmsan_copy_to_user);



/* Functions from kmsan-checks.h follow. */

void kmsan_poison_memory(const void *address, size_t size, gfp_t flags)

{