btrfs: reject invalid compression level

Inspired by recent changes to compression level parsing in
6db1df415d73fc ("btrfs: accept and ignore compression level for lzo")
it turns out that we do not do any extra validation for compression
level input string, thus allowing things like "compress=lzo:invalid" to
be accepted without warnings.

Although we accept levels that are beyond the supported algorithm
ranges, accepting completely invalid level specification is not correct.

Fix the too loose checks for compression level, by doing proper error
handling of kstrtoint(), so that we will reject not only too large
values (beyond int range) but also completely wrong levels like
"lzo:invalid".

Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 13 insertions, 9 deletions

diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index d09d622016ef..35e3071cec06 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -1616,25 +1616,29 @@ out:
 }
 
 /*
- * Convert the compression suffix (eg. after "zlib" starting with ":") to
- * level, unrecognized string will set the default level. Negative level
- * numbers are allowed.
+ * Convert the compression suffix (eg. after "zlib" starting with ":") to level.
+ *
+ * If the resulting level exceeds the algo's supported levels, it will be clamped.
+ *
+ * Return <0 if no valid string can be found.
+ * Return 0 if everything is fine.
  */
-int btrfs_compress_str2level(unsigned int type, const char *str)
+int btrfs_compress_str2level(unsigned int type, const char *str, int *level_ret)
 {
 	int level = 0;
 	int ret;
 
-	if (!type)
+	if (!type) {
+		*level_ret = btrfs_compress_set_level(type, level);
 		return 0;
+	}
 
 	if (str[0] == ':') {
 		ret = kstrtoint(str + 1, 10, &level);
 		if (ret)
-			level = 0;
+			return ret;
 	}
 
-	level = btrfs_compress_set_level(type, level);
-
-	return level;
+	*level_ret = btrfs_compress_set_level(type, level);
+	return 0;
 }