2024-01-04 13:39:30

by Li Lingfeng

Subject: [PATCH] md: use RCU lock to protect traversal in md_spares_need_change()

From: Li Lingfeng <[email protected]>

Since md_start_sync() will be called without the protect of mddev_lock,
and it can run concurrently with array reconfiguration, traversal of rdev
in it should be protected by RCU lock.
Commit bc08041b32ab ("md: suspend array in md_start_sync() if array need
reconfiguration") added md_spares_need_change() to md_start_sync(),
casusing use of rdev without any protection.
Fix this by adding RCU lock in md_spares_need_change().

Fixes: bc08041b32ab ("md: suspend array in md_start_sync() if array need reconfiguration")
Signed-off-by: Li Lingfeng <[email protected]>
---
drivers/md/md.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/md/md.c b/drivers/md/md.c
index 9bdd57324c37..902b43b65052 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -9228,9 +9228,14 @@ static bool md_spares_need_change(struct mddev *mddev)
{
struct md_rdev *rdev;

- rdev_for_each(rdev, mddev)
- if (rdev_removeable(rdev) || rdev_addable(rdev))
+ rcu_read_lock();
+ rdev_for_each_rcu(rdev, mddev) {
+ if (rdev_removeable(rdev) || rdev_addable(rdev)) {
+ rcu_read_unlock();
return true;
+ }
+ }
+ rcu_read_unlock();
return false;
}

--
2.31.1

2024-01-30 07:11:41

by Song Liu

Subject: Re: [PATCH] md: use RCU lock to protect traversal in md_spares_need_change()

On Thu, Jan 4, 2024 at 5:39 AM Li Lingfeng <[email protected]> wrote:
>
> From: Li Lingfeng <[email protected]>
>
> Since md_start_sync() will be called without the protect of mddev_lock,
> and it can run concurrently with array reconfiguration, traversal of rdev
> in it should be protected by RCU lock.
> Commit bc08041b32ab ("md: suspend array in md_start_sync() if array need
> reconfiguration") added md_spares_need_change() to md_start_sync(),
> casusing use of rdev without any protection.
> Fix this by adding RCU lock in md_spares_need_change().
>
> Fixes: bc08041b32ab ("md: suspend array in md_start_sync() if array need reconfiguration")
> Signed-off-by: Li Lingfeng <[email protected]>

Looks good to me. Applied to md-tmp-6.9.

Thanks,
Song