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author | Andrey Ryabinin <aryabinin@virtuozzo.com> | 2018-02-01 19:00:50 +0100 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2018-02-01 21:20:21 +0100 |
commit | 1a3241ff10d038ecd096d03380327f2a0b5840a6 (patch) | |
tree | 0a0529936bc1255b927021cd4a0a3f2cd025c3f7 /lib/string.c | |
parent | compiler.h: Add read_word_at_a_time() function. (diff) | |
download | linux-1a3241ff10d038ecd096d03380327f2a0b5840a6.tar.xz linux-1a3241ff10d038ecd096d03380327f2a0b5840a6.zip |
lib/strscpy: Shut up KASAN false-positives in strscpy()
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>
Diffstat (limited to 'lib/string.c')
-rw-r--r-- | lib/string.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/lib/string.c b/lib/string.c index 64a9e33f1daa..2c0900a5d51a 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); |