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From:   Tomas Bortoli <tomasbortoli@gmail.com>
To:     dhowells@redhat.com
Cc:     linux-cachefs@redhat.com, linux-kernel@vger.kernel.org,
        syzkaller@googlegroups.com, Tomas Bortoli <tomasbortoli@gmail.com>
Subject: [PATCH] fscache: fscache_set_key() - align alloc and usage
Date:   Sun, 22 Jul 2018 13:05:19 +0200
Message-Id: <20180722110519.23917-1-tomasbortoli@gmail.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

The fscache_set_key() function allocates the buf pointer if index_key_len > sizeof(cookie->inline_key).
In such cases the allocated space might not be aligned with the pointer type.
This may result in an out-of-bound in the for-loop later in the same function, as the counter is rounded up.

Signed-off-by: Tomas Bortoli <tomasbortoli@gmail.com>
Reported-by: syzbot+a95b989b2dde8e806af8@syzkaller.appspotmail.com
---
 fs/fscache/cookie.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/fscache/cookie.c b/fs/fscache/cookie.c
index 97137d7ec5ee..ed28bfb6a0fe 100644
--- a/fs/fscache/cookie.c
+++ b/fs/fscache/cookie.c
@@ -98,7 +98,7 @@ static int fscache_set_key(struct fscache_cookie *cookie,
 	cookie->key_len = index_key_len;
 
 	if (index_key_len > sizeof(cookie->inline_key)) {
-		buf = kzalloc(index_key_len, GFP_KERNEL);
+		buf = kzalloc(round_up(index_key_len, sizeof(u32)), GFP_KERNEL);
 		if (!buf)
 			return -ENOMEM;
 		cookie->key = buf;
-- 
2.11.0