diff options
| author | Zhang Yi <yi.zhang@huawei.com> | 2023-06-16 09:55:47 +0800 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2023-06-26 19:36:45 -0400 |
| commit | 31464ab01fff910cb88376384e2b6824f7bf713f (patch) | |
| tree | 8ff3aadc1976d5683364096e36bb04ee9d0bbded | |
| parent | c4d13222afd8a64bf11bc7ec68645496ee8b54b9 (diff) | |
| download | livepatching-31464ab01fff910cb88376384e2b6824f7bf713f.tar.gz | |
jbd2: skip reading super block if it has been verified
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>
| -rw-r--r-- | fs/jbd2/journal.c | 7 |
1 files changed, 3 insertions, 4 deletions
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c index b5e57735ab3faf..559242df0f9a0b 100644 --- a/fs/jbd2/journal.c +++ b/fs/jbd2/journal.c @@ -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)) |