linux-kernel - [PATCH 4.14 79/94] ovl: fix access beyond unterminated strings

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Date:   Mon,  8 Oct 2018 20:32:00 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org,
        syzbot+376cea2b0ef340db3dd4@...kaller.appspotmail.com,
        Amir Goldstein <amir73il@...il.com>,
        Miklos Szeredi <mszeredi@...hat.com>
Subject: [PATCH 4.14 79/94] ovl: fix access beyond unterminated strings

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Amir Goldstein <amir73il@...il.com>

commit 601350ff58d5415a001769532f6b8333820e5786 upstream.

KASAN detected slab-out-of-bounds access in printk from overlayfs,
because string format used %*s instead of %.*s.

> BUG: KASAN: slab-out-of-bounds in string+0x298/0x2d0 lib/vsprintf.c:604
> Read of size 1 at addr ffff8801c36c66ba by task syz-executor2/27811
>
> CPU: 0 PID: 27811 Comm: syz-executor2 Not tainted 4.19.0-rc5+ #36
...
>  printk+0xa7/0xcf kernel/printk/printk.c:1996
>  ovl_lookup_index.cold.15+0xe8/0x1f8 fs/overlayfs/namei.c:689

Reported-by: syzbot+376cea2b0ef340db3dd4@...kaller.appspotmail.com
Signed-off-by: Amir Goldstein <amir73il@...il.com>
Signed-off-by: Miklos Szeredi <mszeredi@...hat.com>
Fixes: 359f392ca53e ("ovl: lookup index entry for copy up origin")
Cc: <stable@...r.kernel.org> # v4.13
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/overlayfs/namei.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -519,7 +519,7 @@ static struct dentry *ovl_lookup_index(s
 			index = NULL;
 			goto out;
 		}
-		pr_warn_ratelimited("overlayfs: failed inode index lookup (ino=%lu, key=%*s, err=%i);\n"
+		pr_warn_ratelimited("overlayfs: failed inode index lookup (ino=%lu, key=%.*s, err=%i);\n"
 				    "overlayfs: mount with '-o index=off' to disable inodes index.\n",
 				    d_inode(origin)->i_ino, name.len, name.name,
 				    err);