From 8dd8b4d7a00d9795e4451c170f5e2aaac2f5aaef Mon Sep 17 00:00:00 2001 From: Andrey Ryabinin Date: Thu, 1 Feb 2018 21:00:50 +0300 Subject: [PATCH] lib/strscpy: Shut up KASAN false-positives in strscpy() [ 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 Signed-off-by: Linus Torvalds Signed-off-by: Sasha Levin --- lib/string.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/string.c b/lib/string.c index 1cd9757291b1..8f1a2a04e22f 100644 --- a/lib/string.c +++ b/lib/string.c @@ -202,7 +202,7 @@ 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); -- 2.11.0