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Subject[PATCH 2/2] md/raid10: fix null-ptr-deref in raid10_sync_request
From: Li Nan <>

init_resync() init mempool and set conf->have_replacemnt at the begaining
of sync, close_sync() free the mempool when sync is completed.

After commit 7e83ccbecd60 ("md/raid10: Allow skipping recovery when clean
arrays are assembled"), recovery might skipped and init_resync() is called
but close_sync() is not. null-ptr-deref occurs as below:
1) creat 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

Fix it by not init_resync() if recovery skipped.

Fixes: 7e83ccbecd60 md/raid10: Allow skipping recovery when clean arrays are assembled")
Signed-off-by: Li Nan <>
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 db9ee3b637d6..9e0e7bf524aa 100644
--- a/drivers/md/raid10.c
+++ b/drivers/md/raid10.c
@@ -3297,10 +3297,6 @@ 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.
@@ -3316,6 +3312,10 @@ 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;
max_sector = mddev->dev_sectors;
if (test_bit(MD_RECOVERY_SYNC, &mddev->recovery) ||
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