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Revert "ext4: fix superblock checksum calculation race"

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This reverts commit acaa532687 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: syzbot+7a4ba6a239b91a126c28@syzkaller.appspotmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Theodore Ts'o 2020-11-11 14:24:18 -05:00
parent a72b38eebe
commit d196e229a8
1 changed files with 0 additions and 11 deletions
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11
fs/ext4/super.c
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@ -289,18 +289,7 @@ void ext4_superblock_csum_set(struct super_block *sb)
if (!ext4_has_metadata_csum(sb)) if (!ext4_has_metadata_csum(sb))
return; 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); 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, ext4_fsblk_t ext4_block_bitmap(struct super_block *sb,