* [PATCH -next 1/2] md: don't dereference mddev after export_rdev()
2023-08-25 2:55 [PATCH -next 0/2] md: fix two regressions related to export_rdev() Yu Kuai
@ 2023-08-25 2:55 ` Yu Kuai
2023-08-25 2:55 ` [PATCH -next 2/2] md: fix warning for holder mismatch from export_rdev() Yu Kuai
2023-08-25 6:38 ` [PATCH -next 0/2] md: fix two regressions related to export_rdev() Song Liu
2 siblings, 0 replies; 4+ messages in thread
From: Yu Kuai @ 2023-08-25 2:55 UTC (permalink / raw)
To: song, yukuai3; +Cc: linux-raid, linux-kernel, yukuai1, yi.zhang, yangerkun
From: Yu Kuai <yukuai3@huawei.com>
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@huawei.com>
---
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 470986943e74..3bb0d9ce0d28 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -840,14 +840,14 @@ 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);
--
2.39.2
^ permalink raw reply related [flat|nested] 4+ messages in thread* [PATCH -next 2/2] md: fix warning for holder mismatch from export_rdev()
2023-08-25 2:55 [PATCH -next 0/2] md: fix two regressions related to export_rdev() Yu Kuai
2023-08-25 2:55 ` [PATCH -next 1/2] md: don't dereference mddev after export_rdev() Yu Kuai
@ 2023-08-25 2:55 ` Yu Kuai
2023-08-25 6:38 ` [PATCH -next 0/2] md: fix two regressions related to export_rdev() Song Liu
2 siblings, 0 replies; 4+ messages in thread
From: Yu Kuai @ 2023-08-25 2:55 UTC (permalink / raw)
To: song, yukuai3; +Cc: linux-raid, linux-kernel, yukuai1, yi.zhang, yangerkun
From: Yu Kuai <yukuai3@huawei.com>
Commit a1d767191096 ("md: use mddev->external to select holder in
export_rdev()") fix the problem that 'claim_rdev' is used for
blkdev_get_by_dev() while 'rdev' is used for blkdev_put().
However, if mddev->external is changed from 0 to 1, then 'rdev' is used
for blkdev_get_by_dev() while 'claim_rdev' is used for blkdev_put(). And
this problem can be reporduced reliably by following:
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:
------------[ cut here ]------------
WARNING: CPU: 0 PID: 960 at block/bdev.c:618 blkdev_put+0x27c/0x330
Modules linked in: multipath md_mod loop
CPU: 0 PID: 960 Comm: test Not tainted 6.5.0-rc2-00121-g01e55c376936-dirty #50
RIP: 0010:blkdev_put+0x27c/0x330
Call Trace:
<TASK>
export_rdev.isra.23+0x50/0xa0 [md_mod]
mddev_unlock+0x19d/0x300 [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 the problem by recording if 'rdev' is used as holder.
Fixes: a1d767191096 ("md: use mddev->external to select holder in export_rdev()")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
---
drivers/md/md.c | 15 ++++++++++++---
drivers/md/md.h | 3 +++
2 files changed, 15 insertions(+), 3 deletions(-)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 3bb0d9ce0d28..278a6e9aad93 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -2494,7 +2494,8 @@ static void export_rdev(struct md_rdev *rdev, struct mddev *mddev)
if (test_bit(AutoDetected, &rdev->flags))
md_autodetect_dev(rdev->bdev->bd_dev);
#endif
- blkdev_put(rdev->bdev, mddev->external ? &claim_rdev : rdev);
+ blkdev_put(rdev->bdev,
+ test_bit(Holder, &rdev->flags) ? rdev : &claim_rdev);
rdev->bdev = NULL;
kobject_put(&rdev->kobj);
}
@@ -3674,6 +3675,7 @@ EXPORT_SYMBOL_GPL(md_rdev_init);
static struct md_rdev *md_import_device(dev_t newdev, int super_format, int super_minor)
{
struct md_rdev *rdev;
+ struct md_rdev *holder;
sector_t size;
int err;
@@ -3688,8 +3690,15 @@ static struct md_rdev *md_import_device(dev_t newdev, int super_format, int supe
if (err)
goto out_clear_rdev;
+ if (super_format == -2) {
+ holder = &claim_rdev;
+ } else {
+ holder = rdev;
+ set_bit(Holder, &rdev->flags);
+ }
+
rdev->bdev = blkdev_get_by_dev(newdev, BLK_OPEN_READ | BLK_OPEN_WRITE,
- super_format == -2 ? &claim_rdev : rdev, NULL);
+ holder, NULL);
if (IS_ERR(rdev->bdev)) {
pr_warn("md: could not open device unknown-block(%u,%u).\n",
MAJOR(newdev), MINOR(newdev));
@@ -3726,7 +3735,7 @@ static struct md_rdev *md_import_device(dev_t newdev, int super_format, int supe
return rdev;
out_blkdev_put:
- blkdev_put(rdev->bdev, super_format == -2 ? &claim_rdev : rdev);
+ blkdev_put(rdev->bdev, holder);
out_clear_rdev:
md_rdev_clear(rdev);
out_free_rdev:
diff --git a/drivers/md/md.h b/drivers/md/md.h
index b365226a4183..b628c292506e 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -211,6 +211,9 @@ enum flag_bits {
* check if there is collision between raid1
* serial bios.
*/
+ Holder, /* rdev is used as holder while opening
+ * underlying disk exclusively.
+ */
};
static inline int is_badblock(struct md_rdev *rdev, sector_t s, int sectors,
--
2.39.2
^ permalink raw reply related [flat|nested] 4+ messages in thread