From f03db98338909e05a6b549696d4eb8bfa5a2a1d6 Mon Sep 17 00:00:00 2001 From: glebius Date: Mon, 15 Oct 2018 20:20:57 +0000 Subject: [PATCH] Avoid OOB reads in memmem(3). commit 51bdcdc424bd7169c8cccdc2de7cad17f5ea0f70 Author: Alexander Monakov Date: Fri Jun 30 00:35:33 2017 +0300 fix OOB reads in Xbyte_memmem Reported by Leah Neukirchen. Reviewed by: emaste Approved by: re (kib) --- lib/libc/string/memmem.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/lib/libc/string/memmem.c b/lib/libc/string/memmem.c index 1a0d18c36533..e0a65a6a3f91 100644 --- a/lib/libc/string/memmem.c +++ b/lib/libc/string/memmem.c @@ -31,27 +31,27 @@ __FBSDID("$FreeBSD$"); static char *twobyte_memmem(const unsigned char *h, size_t k, const unsigned char *n) { uint16_t nw = n[0]<<8 | n[1], hw = h[0]<<8 | h[1]; - for (h++, k--; k; k--, hw = hw<<8 | *++h) - if (hw == nw) return (char *)h-1; - return 0; + for (h+=2, k-=2; k; k--, hw = hw<<8 | *h++) + if (hw == nw) return (char *)h-2; + return hw == nw ? (char *)h-2 : 0; } static char *threebyte_memmem(const unsigned char *h, size_t k, const unsigned char *n) { uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8; uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8; - for (h+=2, k-=2; k; k--, hw = (hw|*++h)<<8) - if (hw == nw) return (char *)h-2; - return 0; + for (h+=3, k-=3; k; k--, hw = (hw|*h++)<<8) + if (hw == nw) return (char *)h-3; + return hw == nw ? (char *)h-3 : 0; } static char *fourbyte_memmem(const unsigned char *h, size_t k, const unsigned char *n) { uint32_t nw = n[0]<<24 | n[1]<<16 | n[2]<<8 | n[3]; uint32_t hw = h[0]<<24 | h[1]<<16 | h[2]<<8 | h[3]; - for (h+=3, k-=3; k; k--, hw = hw<<8 | *++h) - if (hw == nw) return (char *)h-3; - return 0; + for (h+=4, k-=4; k; k--, hw = hw<<8 | *h++) + if (hw == nw) return (char *)h-4; + return hw == nw ? (char *)h-4 : 0; } #define MAX(a,b) ((a)>(b)?(a):(b))