4.4-stable review patch. If anyone has any objections, please let me know.
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From: Jiufei Xue jiufei.xue@linux.alibaba.com
commit fa30dde38aa8628c73a6dded7cb0bba38c27b576 upstream.
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.
Fixes: b436b9bef84d ("ext4: Wait for proper transaction commit on fsync") Signed-off-by: Jiufei Xue jiufei.xue@linux.alibaba.com Signed-off-by: Theodore Ts'o tytso@mit.edu Reviewed-by: Joseph Qi joseph.qi@linux.alibaba.com Cc: stable@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- fs/ext4/ext4_jbd2.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
--- a/fs/ext4/ext4_jbd2.h +++ b/fs/ext4/ext4_jbd2.h @@ -372,7 +372,7 @@ static inline void ext4_update_inode_fsy { 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;