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 <jack@suse.cz>
Link: https://lore.kernel.org/r/20201216101844.22917-4-jack@suse.cz
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 7a890ff..40970a5 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -2978,7 +2978,10 @@ int ext4_orphan_add(handle_t *handle, struct inode *inode)
(le32_to_cpu(sbi->s_es->s_inodes_count))) {
/* Insert this inode at the head of the on-disk orphan list */
NEXT_ORPHAN(inode) = le32_to_cpu(sbi->s_es->s_last_orphan);
+ lock_buffer(sbi->s_sbh);
sbi->s_es->s_last_orphan = cpu_to_le32(inode->i_ino);
+ ext4_superblock_csum_set(sb);
+ unlock_buffer(sbi->s_sbh);
dirty = true;
}
list_add(&EXT4_I(inode)->i_orphan, &sbi->s_orphan);
@@ -3061,7 +3064,10 @@ int ext4_orphan_del(handle_t *handle, struct inode *inode)
mutex_unlock(&sbi->s_orphan_lock);
goto out_brelse;
}
+ lock_buffer(sbi->s_sbh);
sbi->s_es->s_last_orphan = cpu_to_le32(ino_next);
+ ext4_superblock_csum_set(inode->i_sb);
+ unlock_buffer(sbi->s_sbh);
mutex_unlock(&sbi->s_orphan_lock);
err = ext4_handle_dirty_super(handle, inode->i_sb);
} else {
