From: Anand Jain <anand.jain@oracle.com>
Date: Tue, 2 Apr 2019 10:07:38 +0000 (+0800)
Subject: btrfs: prop: fix zstd compression parameter validation
X-Git-Tag: v4.19.35~34
X-Git-Url: http://git.ipfire.org/?p=thirdparty%2Fkernel%2Fstable.git;a=commitdiff_plain;h=fbfbb996d58ebf5ddd0c2ae36efcb7015dc50e95

btrfs: prop: fix zstd compression parameter validation

commit 50398fde997f6be8faebdb5f38e9c9c467370f51 upstream.

We let pass zstd compression parameter even if it is not fully valid.
For example:

  $ btrfs prop set /btrfs compression zst
  $ btrfs prop get /btrfs compression
     compression=zst

zlib and lzo are fine.

Fix it by checking the correct prefix length.

Fixes: 5c1aab1dd544 ("btrfs: Add zstd support")
CC: stable@vger.kernel.org # 4.14+
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Anand Jain <anand.jain@oracle.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c
index dc6140013ae81..fd19f30785667 100644
--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -396,7 +396,7 @@ static int prop_compression_apply(struct inode *inode,
 		btrfs_set_fs_incompat(fs_info, COMPRESS_LZO);
 	} else if (!strncmp("zlib", value, 4)) {
 		type = BTRFS_COMPRESS_ZLIB;
-	} else if (!strncmp("zstd", value, len)) {
+	} else if (!strncmp("zstd", value, 4)) {
 		type = BTRFS_COMPRESS_ZSTD;
 		btrfs_set_fs_incompat(fs_info, COMPRESS_ZSTD);
 	} else {