Re: [PATCHv2] ceph: Fix error handling in ceph_read_iter

From: Yan, Zheng
Date: Mon Oct 10 2016 - 11:10:22 EST



> On 10 Oct 2016, at 21:50, Ilya Dryomov <idryomov@xxxxxxxxx> wrote:
>
> On Mon, Oct 10, 2016 at 3:13 PM, Nikolay Borisov <kernel@xxxxxxxx> wrote:
>>
>>
>> On 10/10/2016 04:11 PM, Yan, Zheng wrote:
>>>
>>>> On 10 Oct 2016, at 20:56, Nikolay Borisov <kernel@xxxxxxxx> wrote:
>>>>
>>>> In case __ceph_do_getattr returns an error and the retry_op in
>>>> ceph_read_iter is not READ_INLINE, then it's possible to invoke
>>>> __free_page on a page which is NULL, this naturally leads to a crash.
>>>> This can happen when, for example, a process waiting on a MDS reply
>>>> receives sigterm.
>>>>
>>>> Fix this by explicitly checking whether the page is set or not.
>>>>
>>>> Signed-off-by: Nikolay Borisov <kernel@xxxxxxxx>
>>>> Link: http://www.spinics.net/lists/ceph-users/msg31592.html
>>>> ---
>>>>
>>>> Inverted the condition, so resending with correct condition
>>>> this time.
>>>>
>>>> fs/ceph/file.c | 3 ++-
>>>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/fs/ceph/file.c b/fs/ceph/file.c
>>>> index 3c68e6aee2f0..7413313ae6c8 100644
>>>> --- a/fs/ceph/file.c
>>>> +++ b/fs/ceph/file.c
>>>> @@ -929,7 +929,8 @@ again:
>>>> statret = __ceph_do_getattr(inode, page,
>>>> CEPH_STAT_CAP_INLINE_DATA, !!page);
>>>> if (statret < 0) {
>>>> - __free_page(page);
>>>> + if (page)
>>>> + __free_page(page);
>>>> if (statret == -ENODATA) {
>>>> BUG_ON(retry_op != READ_INLINE);
>>>> goto again;
>>>> â
>>> Reviewed-by: Yan, Zheng <zyan@xxxxxxxxxx>
>>
>> I believe this needs to also be tagged as stable. To whomever is going
>> to merge it: can you please do that?
>
> I'll do that. Zheng, do you see any other issues with the killable
> wait here?

No. this change is obvious, whatâs your concern?

Regards
Yan, Zheng

>
> Thanks,
>
> Ilya