From: Li Nan <linan122@huawei.com>
Date: Wed, 22 Feb 2023 12:10:00 +0800
Subject: [PATCH] md/raid10: fix null-ptr-deref in raid10_sync_request
References: bsc#1012628
Patch-mainline: 6.3.2
Git-commit: a405c6f0229526160aa3f177f65e20c86fce84c5

commit a405c6f0229526160aa3f177f65e20c86fce84c5 upstream.

init_resync() inits mempool and sets conf->have_replacemnt at the beginning
of sync, close_sync() frees the mempool when sync is completed.

After [1] recovery might be skipped and init_resync() is called but
close_sync() is not. null-ptr-deref occurs with r10bio->dev[i].repl_bio.

The following is one way to reproduce the issue.

  1) create a array, wait for resync to complete, mddev->recovery_cp is set
     to MaxSector.
  2) recovery is woken and it is skipped. conf->have_replacement is set to
     0 in init_resync(). close_sync() not called.
  3) some io errors and rdev A is set to WantReplacement.
  4) a new device is added and set to A's replacement.
  5) recovery is woken, A have replacement, but conf->have_replacemnt is
     0. r10bio->dev[i].repl_bio will not be alloced and null-ptr-deref
     occurs.

Fix it by not calling init_resync() if recovery skipped.

[1] commit 7e83ccbecd60 ("md/raid10: Allow skipping recovery when clean arrays are assembled")
Fixes: 7e83ccbecd60 ("md/raid10: Allow skipping recovery when clean arrays are assembled")
Cc: stable@vger.kernel.org
Signed-off-by: Li Nan <linan122@huawei.com>
Signed-off-by: Song Liu <song@kernel.org>
Link: https://lore.kernel.org/r/20230222041000.3341651-3-linan666@huaweicloud.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 drivers/md/raid10.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c
index 6c66357f..33b0c539 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3289,10 +3289,6 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 	sector_t chunk_mask = conf->geo.chunk_mask;
 	int page_idx = 0;
 
-	if (!mempool_initialized(&conf->r10buf_pool))
-		if (init_resync(conf))
-			return 0;
-
 	/*
 	 * Allow skipping a full rebuild for incremental assembly
 	 * of a clean array, like RAID1 does.
@@ -3308,6 +3304,10 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr,
 		return mddev->dev_sectors - sector_nr;
 	}
 
+	if (!mempool_initialized(&conf->r10buf_pool))
+		if (init_resync(conf))
+			return 0;
+
  skipped:
 	max_sector = mddev->dev_sectors;
 	if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||
-- 
2.35.3