Forwarded: [PATCH] xfs: take hm->lock around __xfs_healthmon_insert() callers

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Subject: [PATCH] xfs: take hm->lock around __xfs_healthmon_insert() callers
Author: kartikey406@xxxxxxxxx

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master


__xfs_healthmon_insert() asserts that hm->lock is held, but both of
its callers invoked it without the lock held:

 - xfs_ioc_health_monitor() inserted the initial RUNNING event right
   after allocating hm, before ever taking the lock.
 - xfs_healthmon_unmount() inserted the UNMOUNT event on an already
   published, shared hm without locking it, racing against
   concurrent event producers on the same monitor.

Take hm->lock around both calls.

Reported-by: syzbot+ccdf3469f5f653bff7ac@xxxxxxxxxxxxxxxxxxxxxxxxx
Closes: https://syzkaller.appspot.com/bug?extid=ccdf3469f5f653bff7ac
Signed-off-by: Deepanshu Kartikey <kartikey406@xxxxxxxxx>
---
 fs/xfs/xfs_healthmon.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/fs/xfs/xfs_healthmon.c b/fs/xfs/xfs_healthmon.c
index 4521ffdab9f1..762f4ce820c8 100644
--- a/fs/xfs/xfs_healthmon.c
+++ b/fs/xfs/xfs_healthmon.c
@@ -415,8 +415,10 @@ xfs_healthmon_unmount(
 	 * There's nothing actionable for userspace after an unmount.  Once
 	 * we've inserted the unmount event, hm no longer owns that event.
 	 */
+	mutex_lock(&hm->lock);
 	__xfs_healthmon_insert(hm, hm->unmount_event);
 	hm->unmount_event = NULL;
+	mutex_unlock(&hm->lock);
 
 	xfs_healthmon_detach(hm);
 	xfs_healthmon_put(hm);
@@ -1213,7 +1215,9 @@ xfs_ioc_health_monitor(
 	}
 	running_event->type = XFS_HEALTHMON_RUNNING;
 	running_event->domain = XFS_HEALTHMON_MOUNT;
+	mutex_lock(&hm->lock);
 	__xfs_healthmon_insert(hm, running_event);
+	mutex_unlock(&hm->lock);
 
 	/*
 	 * Preallocate the unmount event so that we can't fail to notify the
-- 
2.43.0