Commit d196e229 authored by Theodore Ts'o's avatar Theodore Ts'o
Browse files

Revert "ext4: fix superblock checksum calculation race" 

This reverts commit acaa5326 which can
result in a ext4_superblock_csum_set() trying to sleep while a
spinlock is being held.

For more discussion of this issue, please see:

https://lore.kernel.org/r/000000000000f50cb705b313ed70@google.com



Reported-by: default avatar <syzbot+7a4ba6a239b91a126c28@syzkaller.appspotmail.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent a72b38ee

fs/ext4/super.c

+0 −11
Original line number Diff line number Diff line
@@ -289,18 +289,7 @@ void ext4_superblock_csum_set(struct super_block *sb) 
	if (!ext4_has_metadata_csum(sb))

		return;



	/*

	 * Locking the superblock prevents the scenario

	 * where:

	 *  1) a first thread pauses during checksum calculation.

	 *  2) a second thread updates the superblock, recalculates

	 *     the checksum, and updates s_checksum

	 *  3) the first thread resumes and finishes its checksum calculation

	 *     and updates s_checksum with a potentially stale or torn value.

	 */

	lock_buffer(EXT4_SB(sb)->s_sbh);

	es->s_checksum = ext4_superblock_csum(sb, es);

	unlock_buffer(EXT4_SB(sb)->s_sbh);

}



ext4_fsblk_t ext4_block_bitmap(struct super_block *sb,