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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: Alexander Potapenko <glider@google.com>
Reviewed-by: Marco 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Alexander Potapenko 2022-09-15 17:03:52 +02:00 committed by Andrew Morton
parent 3c20650982
commit 75cf029027
3 changed files with 70 additions and 5 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

18
include/linux/instrumented.h
View File

@ -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);
}
/**
@ -162,10 +165,14 @@ instrument_copy_from_user_after(const void *to, const void __user *from,
*
* @to destination variable, may not be address-taken
*/
#define instrument_get_user(to) \
({ \
#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
*
@ -177,8 +184,9 @@ instrument_copy_from_user_after(const void *to, const void __user *from,
* @ptr userspace pointer to copy to
* @size number of bytes to copy
*/
#define instrument_put_user(from, ptr, size) \
({ \
#define instrument_put_user(from, ptr, size) \
({ \
kmsan_copy_to_user(ptr, &from, sizeof(from), 0); \
})
#endif /* _LINUX_INSTRUMENTED_H */

19
include/linux/kmsan-checks.h
View File

@ -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

38
mm/kmsan/hooks.c
View File

@ -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)
{