[PATCH] ceph: Fix error handling in ceph_read_iter

[PATCH] ceph: Fix error handling in ceph_read_iter

[Nikolay Borisov]

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@kyup.com>
Link: http://www.spinics.net/lists/ceph-users/msg31592.html
---
 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;
-- 
2.5.0

[PATCHv2] ceph: Fix error handling in ceph_read_iter

[Nikolay Borisov]

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@kyup.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;
-- 
2.5.0

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

[Yan, Zheng]

> On 10 Oct 2016, at 20:56, Nikolay Borisov <kernel@kyup.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@kyup.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@redhat.com>

> 2.5.0
> 

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

[Nikolay Borisov]

On 10/10/2016 04:11 PM, Yan, Zheng wrote:
> 
>> On 10 Oct 2016, at 20:56, Nikolay Borisov <kernel@kyup.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@kyup.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@redhat.com>

I believe this needs to also be tagged as stable. To whomever is going
to merge it: can you please do that?


> 
>> 2.5.0
>>
> 

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

[Yan, Zheng]

> On 10 Oct 2016, at 21:13, Nikolay Borisov <kernel@kyup.com> wrote:
> 
> 
> 
> On 10/10/2016 04:11 PM, Yan, Zheng wrote:
>> 
>>> On 10 Oct 2016, at 20:56, Nikolay Borisov <kernel@kyup.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@kyup.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@redhat.com>
> 
> I believe this needs to also be tagged as stable. To whomever is going
> to merge it: can you please do that?
> 

need to get it upstream first

> 
>> 
>>> 2.5.0
>>> 
>> 

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

[Ilya Dryomov]

On Mon, Oct 10, 2016 at 3:13 PM, Nikolay Borisov <kernel@kyup.com> wrote:
>
>
> On 10/10/2016 04:11 PM, Yan, Zheng wrote:
>>
>>> On 10 Oct 2016, at 20:56, Nikolay Borisov <kernel@kyup.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@kyup.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@redhat.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?

Thanks,

                Ilya

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

[Yan, Zheng]

> On 10 Oct 2016, at 21:50, Ilya Dryomov <idryomov@gmail.com> wrote:
> 
> On Mon, Oct 10, 2016 at 3:13 PM, Nikolay Borisov <kernel@kyup.com> wrote:
>> 
>> 
>> On 10/10/2016 04:11 PM, Yan, Zheng wrote:
>>> 
>>>> On 10 Oct 2016, at 20:56, Nikolay Borisov <kernel@kyup.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@kyup.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@redhat.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