jbd2: fix data-race and null-ptr-deref in jbd2_journal_dirty_metadata()

Since handle->h_transaction may be a NULL pointer, so we should change it to call is_handle_aborted(handle) first before dereferencing it.

And the following data-race was reported in my fuzzer:

==================================================================

BUG: KCSAN: data-race in jbd2_journal_dirty_metadata / jbd2_journal_dirty_metadata

write to 0xffff888011024104 of 4 bytes by task 10881 on cpu 1:

 jbd2_journal_dirty_metadata+0x2a5/0x770 fs/jbd2/transaction.c:1556
 __ext4_handle_dirty_metadata+0xe7/0x4b0 fs/ext4/ext4_jbd2.c:358
 ext4_do_update_inode fs/ext4/inode.c:5220 [inline]
 ext4_mark_iloc_dirty+0x32c/0xd50 fs/ext4/inode.c:5869
 __ext4_mark_inode_dirty+0xe1/0x450 fs/ext4/inode.c:6074
 ext4_dirty_inode+0x98/0xc0 fs/ext4/inode.c:6103

....

read to 0xffff888011024104 of 4 bytes by task 10880 on cpu 0:

 jbd2_journal_dirty_metadata+0xf2/0x770 fs/jbd2/transaction.c:1512
 __ext4_handle_dirty_metadata+0xe7/0x4b0 fs/ext4/ext4_jbd2.c:358
 ext4_do_update_inode fs/ext4/inode.c:5220 [inline]
 ext4_mark_iloc_dirty+0x32c/0xd50 fs/ext4/inode.c:5869
 __ext4_mark_inode_dirty+0xe1/0x450 fs/ext4/inode.c:6074
 ext4_dirty_inode+0x98/0xc0 fs/ext4/inode.c:6103

....

value changed: 0x00000000 -> 0x00000001
==================================================================

This issue is caused by missing data-race annotation for jh->b_modified. Therefore, the missing annotation needs to be added.

Reported-by [email protected]

Closes https://syzkaller.appspot.com/bug?extid=de24c3fe3c4091051710

Fixes 6e06ae88edae ("jbd2: speedup jbd2_journal_dirty_metadata()")

Signed-off-by Jeongjun Park <[email protected]>

---
v2: Changed to annotate jh->b_modified to avoid performance overhead
- Link to v1: https://lore.kernel.org/all/[email protected]/

---
 fs/jbd2/transaction.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

fs/jbd2/transaction.c +3 -3

index cbc4785462f5..c7867139af69 100644
@@ -1509,7 +1509,7 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
 				jh->b_next_transaction == transaction);
 		spin_unlock(&jh->b_state_lock);
 	}
-	if (jh->b_modified == 1) {
+	if (data_race(jh->b_modified == 1)) {
 		/* If it's in our transaction it must be in BJ_Metadata list. */
 		if (data_race(jh->b_transaction == transaction &&
 		    jh->b_jlist != BJ_Metadata)) {

@@ -1528,7 +1528,6 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
 		goto out;
 	}
 
-	journal = transaction->t_journal;
 	spin_lock(&jh->b_state_lock);
 
 	if (is_handle_aborted(handle)) {

@@ -1543,6 +1542,8 @@ int jbd2_journal_dirty_metadata(handle_t *handle, struct buffer_head *bh)
 		goto out_unlock_bh;
 	}
 
+	journal = transaction->t_journal;
+
 	if (jh->b_modified == 0) {
 		/*
 		 * This buffer's got modified and becoming part
--

Since handle->h_transaction may be a NULL pointer, so we should change it to call is_handle_aborted(handle) first before dereferencing it.

And the following data-race was reported in my fuzzer:

==================================================================

BUG: KCSAN: data-race in jbd2_journal_dirty_metadata / jbd2_journal_dirty_metadata

[...]