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md/raid1: fix NULL pointer dereference

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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>
This commit is contained in:
Yufen Yu 2018-02-24 12:05:56 +08:00 committed by Shaohua Li
parent 8876391e44
commit 3de59bb9d5
1 changed files with 11 additions and 0 deletions
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11
drivers/md/raid1.c
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@ -1809,6 +1809,17 @@ static int raid1_remove_disk(struct mddev *mddev, struct md_rdev *rdev)
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;