From 601350ff58d5415a001769532f6b8333820e5786 Mon Sep 17 00:00:00 2001
From: Amir Goldstein <amir73il@gmail.com>
Date: Fri, 28 Sep 2018 21:00:48 +0300
Subject: [PATCH] ovl: fix access beyond unterminated strings
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@syzkaller.appspotmail.com
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
Fixes: 359f392ca53e ("ovl: lookup index entry for copy up origin")
Cc: <stable@vger.kernel.org> # v4.13
---
fs/overlayfs/namei.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index f28711846dd6e..9c0ca6a7becfb 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -686,7 +686,7 @@ struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper,
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);
--
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