From 23c19e2ca736722a9523b64b07cda7efab7b6c57 Mon Sep 17 00:00:00 2001
From: Dmitry Kasatkin <d.kasatkin@samsung.com>
Date: Fri, 15 Aug 2014 13:28:52 +0300
Subject: ima: prevent buffer overflow in ima_alloc_tfm()

This patch fixes the case where the file's signature/hash xattr contains
an invalid hash algorithm.  Although we can not verify the xattr, we still
need to measure the file.  Use the default IMA hash algorithm.

Signed-off-by: Dmitry Kasatkin <d.kasatkin@samsung.com>
Signed-off-by: Mimi Zohar <zohar@linux.vnet.ibm.com>

diff --git a/security/integrity/ima/ima_crypto.c b/security/integrity/ima/ima_crypto.c
index 2d103dc..1178b30 100644
--- a/security/integrity/ima/ima_crypto.c
+++ b/security/integrity/ima/ima_crypto.c
@@ -116,7 +116,10 @@ static struct crypto_shash *ima_alloc_tfm(enum hash_algo algo)
 	struct crypto_shash *tfm = ima_shash_tfm;
 	int rc;
 
-	if (algo != ima_hash_algo && algo < HASH_ALGO__LAST) {
+	if (algo < 0 || algo >= HASH_ALGO__LAST)
+		algo = ima_hash_algo;
+
+	if (algo != ima_hash_algo) {
 		tfm = crypto_alloc_shash(hash_algo_name[algo], 0, 0);
 		if (IS_ERR(tfm)) {
 			rc = PTR_ERR(tfm);
-- 
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