From 99fed74ba7866f385637fb124d2b58eb87058f7c Mon Sep 17 00:00:00 2001 From: ume Date: Tue, 12 Aug 2014 13:09:32 +0000 Subject: Fix broken pointer overflow check ns_name_unpack() Many compilers may optimize away the overflow check `msg + l < msg', where `msg' is a pointer and `l' is an integer, because pointer overflow is undefined behavior in C. Use a safe precondition test `l >= eom - msg' instead. Reference: https://android-review.googlesource.com/#/c/50570/ Requested by: pfg Obtained from: NetBSD (CVS rev. 1.10) --- lib/libc/nameser/ns_name.c | 5 +++-- 1 file changed, 3 insertions(+), 2 deletions(-) (limited to 'lib') diff --git a/lib/libc/nameser/ns_name.c b/lib/libc/nameser/ns_name.c index 1f37406..5b8a8cb 100644 --- a/lib/libc/nameser/ns_name.c +++ b/lib/libc/nameser/ns_name.c @@ -463,11 +463,12 @@ ns_name_unpack2(const u_char *msg, const u_char *eom, const u_char *src, } if (len < 0) len = srcp - src + 1; - srcp = msg + (((n & 0x3f) << 8) | (*srcp & 0xff)); - if (srcp < msg || srcp >= eom) { /*%< Out of range. */ + l = ((n & 0x3f) << 8) | (*srcp & 0xff); + if (l >= eom - msg) { /*%< Out of range. */ errno = EMSGSIZE; return (-1); } + srcp = msg + l; checked += 2; /* * Check for loops in the compressed name; -- cgit v1.1