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Fix out-of-bounds read in libc/regex.

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The bug is an out-of-bounds read detected with address sanitizer that
happens when 'sp' in p_b_coll_elems() includes NUL byte[s], e.g. if it's
equal to "GS\x00". In that case len will be equal to 4, and the
strncmp(cp->name, sp, len) call will succeed when cp->name is "GS" but the
cp->name[len] == '\0' comparison will cause the read to go out-of-bounds.

Checking the length using strlen() instead eliminates the issue.

The bug was found in LLVM with oss-fuzz:
	https://reviews.llvm.org/D39380

MFC after:	1 week
Obtained from:	Vlad Tsyrklevich through posting on openbsd-tech
This commit is contained in:
Pedro F. Giffuni 2017-10-28 20:09:34 +00:00
parent 3faac3ea79
commit 0f23ab8aac
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=325066
1 changed files with 1 additions and 1 deletions
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2
lib/libc/regex/regcomp.c
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@ -1059,7 +1059,7 @@ p_b_coll_elem(struct parse *p,
}
len = p->next - sp;
for (cp = cnames; cp->name != NULL; cp++)
if (strncmp(cp->name, sp, len) == 0 && cp->name[len] == '\0')
if (strncmp(cp->name, sp, len) == 0 && strlen(cp->name) == len)
return(cp->code); /* known name */
memset(&mbs, 0, sizeof(mbs));
if ((clen = mbrtowc(&wc, sp, len, &mbs)) == len)