[PATCH 5.0 076/117] btrfs: prop: fix vanished compression property after failed set

Greg Kroah-Hartman
2019-04-15T19:13:34Z

From: Anand Jain <anand.jain@oracle.com>

commit 272e5326c7837697882ce3162029ba893059b616 upstream.

The compression property resets to NULL, instead of the old value if we
fail to set the new compression parameter.

$ btrfs prop get /btrfs compression
compression=lzo
$ btrfs prop set /btrfs compression zli
ERROR: failed to set compression for /btrfs: Invalid argument
$ btrfs prop get /btrfs compression

This is because the compression property ->validate() is successful for
'zli' as the strncmp() used the length passed from the userspace.

Fix it by using the expected string length in strncmp().

Fixes: 63541927c8d1 ("Btrfs: add support for inode properties")
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>

---
fs/btrfs/props.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

--- a/fs/btrfs/props.c
+++ b/fs/btrfs/props.c
@@ -366,11 +366,11 @@ int btrfs_subvol_inherit_props(struct bt

static int prop_compression_validate(const char *value, size_t len)
{
- if (!strncmp("lzo", value, len))
+ if (!strncmp("lzo", value, 3))
return 0;
- else if (!strncmp("zlib", value, len))
+ else if (!strncmp("zlib", value, 4))
return 0;
- else if (!strncmp("zstd", value, len))
+ else if (!strncmp("zstd", value, 4))
return 0;

return -EINVAL;