6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Yu Kuai <yukuai3@xxxxxxxxxx>
[ Upstream commit 7deac114be5fb25a4e865212ed0feaf5f85f2a28 ]
Except for initial reference, mddev->kobject is referenced by
rdev->kobject, and if the last rdev is freed, there is no guarantee that
mddev is still valid. Hence mddev should not be used anymore after
export_rdev().
This problem can be triggered by following test for mdadm at very
low rate:
New file: mdadm/tests/23rdev-lifetime
devname=${dev0##*/}
devt=`cat /sys/block/$devname/dev`
pid=""
runtime=2
clean_up_test() {
pill -9 $pid
echo clear > /sys/block/md0/md/array_state
}
trap 'clean_up_test' EXIT
add_by_sysfs() {
while true; do
echo $devt > /sys/block/md0/md/new_dev
done
}
remove_by_sysfs(){
while true; do
echo remove > /sys/block/md0/md/dev-${devname}/state
done
}
echo md0 > /sys/module/md_mod/parameters/new_array || die "create md0 failed"
add_by_sysfs &
pid="$pid $!"
remove_by_sysfs &
pid="$pid $!"
sleep $runtime
exit 0
Test cmd:
./test --save-logs --logdir=/tmp/ --keep-going --dev=loop --tests=23rdev-lifetime
Test result:
general protection fault, probably for non-canonical address 0x6b6b6b6b6b6b6bcb: 0000 [#4] PREEMPT SMP
CPU: 0 PID: 1292 Comm: test Tainted: G D W 6.5.0-rc2-00121-g01e55c376936 #562
RIP: 0010:md_wakeup_thread+0x9e/0x320 [md_mod]
Call Trace:
<TASK>
mddev_unlock+0x1b6/0x310 [md_mod]
rdev_attr_store+0xec/0x190 [md_mod]
sysfs_kf_write+0x52/0x70
kernfs_fop_write_iter+0x19a/0x2a0
vfs_write+0x3b5/0x770
ksys_write+0x74/0x150
__x64_sys_write+0x22/0x30
do_syscall_64+0x40/0x90
entry_SYSCALL_64_after_hwframe+0x63/0xcd
Fix this problem by don't dereference mddev after export_rdev().
Fixes: 3ce94ce5d05a ("md: fix duplicate filename for rdev")
Signed-off-by: Yu Kuai <yukuai3@xxxxxxxxxx>
Signed-off-by: Song Liu <song@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20230825025532.1523008-2-yukuai1@xxxxxxxxxxxxxxx
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/md/md.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 2a4a3d3039fae..fba2809cd384a 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -798,14 +798,14 @@ void mddev_unlock(struct mddev *mddev)
} else
mutex_unlock(&mddev->reconfig_mutex);
+ md_wakeup_thread(mddev->thread);
+ wake_up(&mddev->sb_wait);
+
list_for_each_entry_safe(rdev, tmp, &delete, same_set) {
list_del_init(&rdev->same_set);
kobject_del(&rdev->kobj);
export_rdev(rdev, mddev);
}
-
- md_wakeup_thread(mddev->thread);
- wake_up(&mddev->sb_wait);
}
EXPORT_SYMBOL_GPL(mddev_unlock);
--
2.40.1
