linux-kernel - [PATCH] zlib inflate: Fix potential buffer overflow

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Date:   Mon,  3 Apr 2017 09:14:19 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-kernel@...r.kernel.org, Guenter Roeck <linux@...ck-us.net>
Subject: [PATCH] zlib inflate: Fix potential buffer overflow

smatch says:

lib/zlib_inflate/inftrees.c:240 zlib_inflate_table() error:
	buffer overflow 'count' 16 <= 16

The loop calculating the value for 'min', which is later used to access
count[], can indeed result in an index larger than ARRAY_SIZE(count)
if the array is filled with 0.

Fixes: 4f3865fb57a04 ("zlib_inflate: Upgrade library code to a recent version")
Signed-off-by: Guenter Roeck <linux@...ck-us.net>
---
 lib/zlib_inflate/inftrees.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/zlib_inflate/inftrees.c b/lib/zlib_inflate/inftrees.c
index 3fe6ce5b53e5..028943052926 100644
--- a/lib/zlib_inflate/inftrees.c
+++ b/lib/zlib_inflate/inftrees.c
@@ -109,7 +109,7 @@ int zlib_inflate_table(codetype type, unsigned short *lens, unsigned codes,
         *bits = 1;
         return 0;     /* no symbols, but wait for decoding to report error */
     }
-    for (min = 1; min <= MAXBITS; min++)
+    for (min = 1; min < MAXBITS; min++)
         if (count[min] != 0) break;
     if (root < min) root = min;
 
-- 
2.7.4