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authorLinus Torvalds <torvalds@linux-foundation.org>2009-11-18 22:31:52 +0100
committerLinus Torvalds <torvalds@linux-foundation.org>2009-11-18 17:18:13 -0800
commita414f01ac2899f273ef8fe98fa44158ac12793f2 (patch)
tree30a7ef8d7d2f8d4aca0781fa8785630fc1f6320d
parent6602b355c2cf8f4c628732827408606075288d28 (diff)
downloadlinux-stericsson-a414f01ac2899f273ef8fe98fa44158ac12793f2.tar.gz
strcmp: fix overflow and possibly signedness error
Doing the strcmp return value as signed char __res = *cs - *ct; is wrong for two reasons. The subtraction can overflow because __res doesn't use a type big enough. Moreover the compared bytes should be interpreted as unsigned char as specified by POSIX. The same problem is fixed in strncmp. Signed-off-by: Uwe Kleine-K├Ânig <u.kleine-koenig@pengutronix.de> Cc: Michael Buesch <mb@bu3sch.de> Cc: Andreas Schwab <schwab@linux-m68k.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
-rw-r--r--lib/string.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/lib/string.c b/lib/string.c
index b19b87af65a3..e96421ab9a9a 100644
--- a/lib/string.c
+++ b/lib/string.c
@@ -246,13 +246,17 @@ EXPORT_SYMBOL(strlcat);
#undef strcmp
int strcmp(const char *cs, const char *ct)
{
- signed char __res;
+ unsigned char c1, c2;
while (1) {
- if ((__res = *cs - *ct++) != 0 || !*cs++)
+ c1 = *cs++;
+ c2 = *ct++;
+ if (c1 != c2)
+ return c1 < c2 ? -1 : 1;
+ if (!c1)
break;
}
- return __res;
+ return 0;
}
EXPORT_SYMBOL(strcmp);
#endif
@@ -266,14 +270,18 @@ EXPORT_SYMBOL(strcmp);
*/
int strncmp(const char *cs, const char *ct, size_t count)
{
- signed char __res = 0;
+ unsigned char c1, c2;
while (count) {
- if ((__res = *cs - *ct++) != 0 || !*cs++)
+ c1 = *cs++;
+ c2 = *ct++;
+ if (c1 != c2)
+ return c1 < c2 ? -1 : 1;
+ if (!c1)
break;
count--;
}
- return __res;
+ return 0;
}
EXPORT_SYMBOL(strncmp);
#endif