4.4-stable review patch. If anyone has any objections, please let me know.
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From: Yufen Yu yuyufen@huawei.com
[ Upstream commit 3de59bb9d551428cbdc76a9ea57883f82e350b4d ]
In handle_write_finished(), if r1_bio->bios[m] != NULL, it thinks the corresponding conf->mirrors[m].rdev is also not NULL. But, it is not always true.
Even if some io hold replacement rdev(i.e. rdev->nr_pending.count > 0), raid1_remove_disk() can also set the rdev as NULL. That means, bios[m] != NULL, but mirrors[m].rdev is NULL, resulting in NULL pointer dereference in handle_write_finished and sync_request_write.
This patch can fix BUGs as follows:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000140 IP: [<ffffffff815bbbbd>] raid1d+0x2bd/0xfc0 PGD 12ab52067 PUD 12f587067 PMD 0 Oops: 0000 [#1] SMP CPU: 1 PID: 2008 Comm: md3_raid1 Not tainted 4.1.44+ #130 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc26 04/01/2014 Call Trace: ? schedule+0x37/0x90 ? prepare_to_wait_event+0x83/0xf0 md_thread+0x144/0x150 ? wake_atomic_t_function+0x70/0x70 ? md_start_sync+0xf0/0xf0 kthread+0xd8/0xf0 ? kthread_worker_fn+0x160/0x160 ret_from_fork+0x42/0x70 ? kthread_worker_fn+0x160/0x160
BUG: unable to handle kernel NULL pointer dereference at 00000000000000b8 IP: sync_request_write+0x9e/0x980 PGD 800000007c518067 P4D 800000007c518067 PUD 8002b067 PMD 0 Oops: 0000 [#1] SMP PTI CPU: 24 PID: 2549 Comm: md3_raid1 Not tainted 4.15.0+ #118 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1.fc26 04/01/2014 Call Trace: ? sched_clock+0x5/0x10 ? sched_clock_cpu+0xc/0xb0 ? flush_pending_writes+0x3a/0xd0 ? pick_next_task_fair+0x4d5/0x5f0 ? __switch_to+0xa2/0x430 raid1d+0x65a/0x870 ? find_pers+0x70/0x70 ? find_pers+0x70/0x70 ? md_thread+0x11c/0x160 md_thread+0x11c/0x160 ? finish_wait+0x80/0x80 kthread+0x111/0x130 ? kthread_create_worker_on_cpu+0x70/0x70 ? do_syscall_64+0x6f/0x190 ? SyS_exit_group+0x10/0x10 ret_from_fork+0x35/0x40
Reviewed-by: NeilBrown neilb@suse.com Signed-off-by: Yufen Yu yuyufen@huawei.com Signed-off-by: Shaohua Li sh.li@alibaba-inc.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/md/raid1.c | 11 +++++++++++ 1 file changed, 11 insertions(+)
--- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -1686,6 +1686,17 @@ static int raid1_remove_disk(struct mdde struct md_rdev *repl = conf->mirrors[conf->raid_disks + number].rdev; freeze_array(conf, 0); + if (atomic_read(&repl->nr_pending)) { + /* It means that some queued IO of retry_list + * hold repl. Thus, we cannot set replacement + * as NULL, avoiding rdev NULL pointer + * dereference in sync_request_write and + * handle_write_finished. + */ + err = -EBUSY; + unfreeze_array(conf); + goto abort; + } clear_bit(Replacement, &repl->flags); p->rdev = repl; conf->mirrors[conf->raid_disks + number].rdev = NULL;