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jbd2: skip reading super block if it has been verified

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We got a NULL pointer dereference issue below while running generic/475
I/O failure pressure test.

 BUG: kernel NULL pointer dereference, address: 0000000000000000
 #PF: supervisor write access in kernel mode
 #PF: error_code(0x0002) - not-present page
 PGD 0 P4D 0
 Oops: 0002 [#1] PREEMPT SMP PTI
 CPU: 1 PID: 15600 Comm: fsstress Not tainted 6.4.0-rc5-xfstests-00055-gd3ab1bca26b4 #190
 RIP: 0010:jbd2_journal_set_features+0x13d/0x430
 ...
 Call Trace:
  <TASK>
  ? __die+0x23/0x60
  ? page_fault_oops+0xa4/0x170
  ? exc_page_fault+0x67/0x170
  ? asm_exc_page_fault+0x26/0x30
  ? jbd2_journal_set_features+0x13d/0x430
  jbd2_journal_revoke+0x47/0x1e0
  __ext4_forget+0xc3/0x1b0
  ext4_free_blocks+0x214/0x2f0
  ext4_free_branches+0xeb/0x270
  ext4_ind_truncate+0x2bf/0x320
  ext4_truncate+0x1e4/0x490
  ext4_handle_inode_extension+0x1bd/0x2a0
  ? iomap_dio_complete+0xaf/0x1d0

The root cause is the journal super block had been failed to write out
due to I/O fault injection, it's uptodate bit was cleared by
end_buffer_write_sync() and didn't reset yet in jbd2_write_superblock().
And it raced by journal_get_superblock()->bh_read(), unfortunately, the
read IO is also failed, so the error handling in
journal_fail_superblock() unexpectedly clear the journal->j_sb_buffer,
finally lead to above NULL pointer dereference issue.

If the journal super block had been read and verified, there is no need
to call bh_read() read it again even if it has been failed to written
out. So the fix could be simply move buffer_verified(bh) in front of
bh_read(). Also remove a stale comment left in
jbd2_journal_check_used_features().

Fixes: 51bacdba23d8 ("jbd2: factor out journal initialization from journal_get_superblock()")
Reported-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20230616015547.3155195-1-yi.zhang@huaweicloud.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Zhang Yi 2023-06-16 09:55:47 +08:00 committed by Theodore Ts'o
parent c4d13222af
commit 31464ab01f
1 changed files with 3 additions and 4 deletions
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7
fs/jbd2/journal.c
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@ -1919,6 +1919,9 @@ static int journal_get_superblock(journal_t *journal)
bh = journal->j_sb_buffer;
J_ASSERT(bh != NULL);
if (buffer_verified(bh))
return 0;
err = bh_read(bh, 0);
if (err < 0) {
printk(KERN_ERR
@ -1926,9 +1929,6 @@ static int journal_get_superblock(journal_t *journal)
goto out;
}
if (buffer_verified(bh))
return 0;
sb = journal->j_superblock;
err = -EINVAL;
@ -2229,7 +2229,6 @@ int jbd2_journal_check_used_features(journal_t *journal, unsigned long compat,
if (!compat && !ro && !incompat)
return 1;
/* Load journal superblock if it is not loaded yet. */
if (journal_get_superblock(journal))
return 0;
if (!jbd2_format_support_feature(journal))