[ Upstream commit 1a3241ff10d038ecd096d03380327f2a0b5840a6 ]
strscpy() performs the word-at-a-time optimistic reads. So it may may access the memory past the end of the object, which is perfectly fine since strscpy() doesn't use that (past-the-end) data and makes sure the optimistic read won't cross a page boundary.
Use new read_word_at_a_time() to shut up the KASAN.
Note that this potentially could hide some bugs. In example bellow, stscpy() will copy more than we should (1-3 extra uninitialized bytes):
char dst[8]; char *src;
src = kmalloc(5, GFP_KERNEL); memset(src, 0xff, 5); strscpy(dst, src, 8);
Signed-off-by: Andrey Ryabinin aryabinin@virtuozzo.com Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Sasha Levin sashal@kernel.org --- lib/string.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/lib/string.c b/lib/string.c index 1530643edf00..33befc6ba3fa 100644 --- a/lib/string.c +++ b/lib/string.c @@ -203,7 +203,7 @@ ssize_t strscpy(char *dest, const char *src, size_t count) while (max >= sizeof(unsigned long)) { unsigned long c, data;
- c = *(unsigned long *)(src+res); + c = read_word_at_a_time(src+res); if (has_zero(c, &data, &constants)) { data = prep_zero_mask(c, data, &constants); data = create_zero_mask(data);