linux-kernel - Re: [PATCHv2] ceph: Fix error handling in ceph_read

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Date:   Mon, 10 Oct 2016 23:09:52 +0800
From:   "Yan, Zheng" <zyan@...hat.com>
To:     Ilya Dryomov <idryomov@...il.com>
Cc:     Nikolay Borisov <kernel@...p.com>,
        ceph-devel <ceph-devel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCHv2] ceph: Fix error handling in ceph_read_iter


> On 10 Oct 2016, at 21:50, Ilya Dryomov <idryomov@...il.com> wrote:
> 
> On Mon, Oct 10, 2016 at 3:13 PM, Nikolay Borisov <kernel@...p.com> wrote:
>> 
>> 
>> On 10/10/2016 04:11 PM, Yan, Zheng wrote:
>>> 
>>>> On 10 Oct 2016, at 20:56, Nikolay Borisov <kernel@...p.com> 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@...p.com>
>>>> 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;
>>>> —
>>> Reviewed-by: Yan, Zheng <zyan@...hat.com>
>> 
>> 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, what’s your concern?

Regards
Yan, Zheng

> 
> Thanks,
> 
>                Ilya