Re: [PATCH v2] md: add mddev->pers to avoid potential NULL pointer dereference

[Song Liu <songliubraving@fb.com>]

> On Apr 2, 2019, at 2:11 PM, NeilBrown <neilb@suse.com> wrote:
> 
> On Tue, Apr 02 2019, Yufen Yu wrote:
> 
>> When doing re-add, we need to ensure rdev->mddev->pers is not NULL,
>> which can avoid potential NULL pointer derefence in fallowing
>> add_bound_rdev().
>> 
>> Fixes: a6da4ef85cef ("md: re-add a failed disk")
>> Cc: Xiao Ni <xni@redhat.com>
>> Cc: NeilBrown <neilb@suse.com>
>> Cc: <stable@vger.kernel.org>
>> Signed-off-by: Yufen Yu <yuyufen@huawei.com>
> 
> Reviewed-by: NeilBrown <neilb@suse.com>
> 
> Thanks,
> NeilBrown

Thanks Yufen and Neil. 

I applied it to the md-next branch:

https://github.com/liu-song-6/linux/tree/md-next

Song

> 
>> ---
>> drivers/md/md.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>> 
>> diff --git a/drivers/md/md.c b/drivers/md/md.c
>> index 875b29ba5926..66b6bdf9f364 100644
>> --- a/drivers/md/md.c
>> +++ b/drivers/md/md.c
>> @@ -2859,8 +2859,10 @@ state_store(struct md_rdev *rdev, const char *buf, size_t len)
>> 			err = 0;
>> 		}
>> 	} else if (cmd_match(buf, "re-add")) {
>> -		if (test_bit(Faulty, &rdev->flags) && (rdev->raid_disk == -1) &&
>> -			rdev->saved_raid_disk >= 0) {
>> +		if (!rdev->mddev->pers)
>> +			err = -EINVAL;
>> +		else if (test_bit(Faulty, &rdev->flags) && (rdev->raid_disk == -1) &&
>> +				rdev->saved_raid_disk >= 0) {
>> 			/* clear_bit is performed _after_ all the devices
>> 			 * have their local Faulty bit cleared. If any writes
>> 			 * happen in the meantime in the local node, they
>> -- 
>> 2.16.2.dirty