linux-ext4 - [PATCH] ext4: fix NULL pointer dereference while journal is aborted

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Date:   Mon, 11 Mar 2019 14:35:28 +0800
From:   Jiufei Xue <jiufei.xue@...ux.alibaba.com>
To:     linux-ext4@...r.kernel.org
Cc:     tytso@....edu, joseph.qi@...ux.alibaba.com
Subject: [PATCH] ext4: fix NULL pointer dereference while journal is aborted

We see the following NULL pointer dereference while running xfstests
generic/475:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
PGD 8000000c84bad067 P4D 8000000c84bad067 PUD c84e62067 PMD 0
Oops: 0000 [#1] SMP PTI
CPU: 7 PID: 9886 Comm: fsstress Kdump: loaded Not tainted 5.0.0-rc8 #10
RIP: 0010:ext4_do_update_inode+0x4ec/0x760
...
Call Trace:
? jbd2_journal_get_write_access+0x42/0x50
? __ext4_journal_get_write_access+0x2c/0x70
? ext4_truncate+0x186/0x3f0
ext4_mark_iloc_dirty+0x61/0x80
ext4_mark_inode_dirty+0x62/0x1b0
ext4_truncate+0x186/0x3f0
? unmap_mapping_pages+0x56/0x100
ext4_setattr+0x817/0x8b0
notify_change+0x1df/0x430
do_truncate+0x5e/0x90
? generic_permission+0x12b/0x1a0

This is triggered because the NULL pointer handle->h_transaction was
dereferenced in function ext4_update_inode_fsync_trans().
I found that the h_transaction was set to NULL in jbd2__journal_restart
but failed to attached to a new transaction while the journal is aborted.

Fix this by checking the handle before updating the inode.

Signed-off-by: Jiufei Xue <jiufei.xue@...ux.alibaba.com>
---
 fs/ext4/ext4_jbd2.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/ext4/ext4_jbd2.h b/fs/ext4/ext4_jbd2.h
index a1ac7e9245ec..75a5309f2231 100644
--- a/fs/ext4/ext4_jbd2.h
+++ b/fs/ext4/ext4_jbd2.h
@@ -384,7 +384,7 @@ static inline void ext4_update_inode_fsync_trans(handle_t *handle,
 {
 	struct ext4_inode_info *ei = EXT4_I(inode);

-	if (ext4_handle_valid(handle)) {
+	if (ext4_handle_valid(handle) && !is_handle_aborted(handle)) {
 		ei->i_sync_tid = handle->h_transaction->t_tid;
 		if (datasync)
 			ei->i_datasync_tid = handle->h_transaction->t_tid;
-- 
2.19.1.856.g8858448bb