From 05c2c00f3769abb9e323fcaca70d2de0b48af7ba Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Wed, 16 Dec 2020 11:18:39 +0100 Subject: ext4: protect superblock modifications with a buffer lock Protect all superblock modifications (including checksum computation) with a superblock buffer lock. That way we are sure computed checksum matches current superblock contents (a mismatch could cause checksum failures in nojournal mode or if an unjournalled superblock update races with a journalled one). Also we avoid modifying superblock contents while it is being written out (which can cause DIF/DIX failures if we are running in nojournal mode). Signed-off-by: Jan Kara Link: https://lore.kernel.org/r/20201216101844.22917-4-jack@suse.cz Signed-off-by: Theodore Ts'o --- fs/ext4/xattr.c | 3 +++ 1 file changed, 3 insertions(+) (limited to 'fs/ext4/xattr.c') diff --git a/fs/ext4/xattr.c b/fs/ext4/xattr.c index 4e3b1f8c2e81..1db7ca778d69 100644 --- a/fs/ext4/xattr.c +++ b/fs/ext4/xattr.c @@ -792,7 +792,10 @@ static void ext4_xattr_update_super_block(handle_t *handle, BUFFER_TRACE(EXT4_SB(sb)->s_sbh, "get_write_access"); if (ext4_journal_get_write_access(handle, EXT4_SB(sb)->s_sbh) == 0) { + lock_buffer(EXT4_SB(sb)->s_sbh); ext4_set_feature_xattr(sb); + ext4_superblock_csum_set(sb); + unlock_buffer(EXT4_SB(sb)->s_sbh); ext4_handle_dirty_super(handle, sb); } } -- cgit v1.2.3