diff options
| author | Jiasheng Jiang <jiashengjiangcool@gmail.com> | 2026-01-17 14:59:03 +0000 |
|---|---|---|
| committer | Sasha Levin <sashal@kernel.org> | 2026-03-04 07:19:39 -0500 |
| commit | dceb5a843910004cb118148e267036104fc3ee43 (patch) | |
| tree | 5cc50bce077c677abc128981992e42e7fde6276b /drivers/md | |
| parent | bab8d762a8dbb816b10011e13b87d1bca91e5f77 (diff) | |
md-cluster: fix NULL pointer dereference in process_metadata_update
[ Upstream commit f150e753cb8dd756085f46e86f2c35ce472e0a3c ]
The function process_metadata_update() blindly dereferences the 'thread'
pointer (acquired via rcu_dereference_protected) within the wait_event()
macro.
While the code comment states "daemon thread must exist", there is a valid
race condition window during the MD array startup sequence (md_run):
1. bitmap_load() is called, which invokes md_cluster_ops->join().
2. join() starts the "cluster_recv" thread (recv_daemon).
3. At this point, recv_daemon is active and processing messages.
4. However, mddev->thread (the main MD thread) is not initialized until
later in md_run().
If a METADATA_UPDATED message is received from a remote node during this
specific window, process_metadata_update() will be called while
mddev->thread is still NULL, leading to a kernel panic.
To fix this, we must validate the 'thread' pointer. If it is NULL, we
release the held lock (no_new_dev_lockres) and return early, safely
ignoring the update request as the array is not yet fully ready to
process it.
Link: https://lore.kernel.org/linux-raid/20260117145903.28921-1-jiashengjiangcool@gmail.com
Signed-off-by: Jiasheng Jiang <jiashengjiangcool@gmail.com>
Signed-off-by: Yu Kuai <yukuai@fnnas.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'drivers/md')
| -rw-r--r-- | drivers/md/md-cluster.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/md/md-cluster.c b/drivers/md/md-cluster.c index 11f1e91d387d..896279988dfd 100644 --- a/drivers/md/md-cluster.c +++ b/drivers/md/md-cluster.c @@ -549,8 +549,13 @@ static void process_metadata_update(struct mddev *mddev, struct cluster_msg *msg dlm_lock_sync(cinfo->no_new_dev_lockres, DLM_LOCK_CR); - /* daemaon thread must exist */ thread = rcu_dereference_protected(mddev->thread, true); + if (!thread) { + pr_warn("md-cluster: Received metadata update but MD thread is not ready\n"); + dlm_unlock_sync(cinfo->no_new_dev_lockres); + return; + } + wait_event(thread->wqueue, (got_lock = mddev_trylock(mddev)) || test_bit(MD_CLUSTER_HOLDING_MUTEX_FOR_RECVD, &cinfo->state)); |