2021-12-09 02:51:08

by Jiasheng Jiang

Subject: [PATCH] libceph, ceph: potential dereference of null pointer

The return value of kzalloc() needs to be checked.
To avoid use of null pointer in case of the failure of alloc.

Fixes: 3d14c5d2b6e1 ("ceph: factor out libceph from Ceph file system")
Signed-off-by: Jiasheng Jiang <[email protected]>
---
net/ceph/osd_client.c | 2 ++
1 file changed, 2 insertions(+)

diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index ff8624a7c964..3203e8a34370 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -1234,6 +1234,8 @@ static struct ceph_osd *create_osd(struct ceph_osd_client *osdc, int onum)
WARN_ON(onum == CEPH_HOMELESS_OSD);

osd = kzalloc(sizeof(*osd), GFP_NOIO | __GFP_NOFAIL);
+ if (!osd)
+ return NULL;
osd_init(osd);
osd->o_osdc = osdc;
osd->o_osd = onum;
--
2.25.1

2021-12-09 11:20:50

by Jeff Layton

Subject: Re: [PATCH] libceph, ceph: potential dereference of null pointer

On Thu, 2021-12-09 at 10:50 +0800, Jiasheng Jiang wrote:
> The return value of kzalloc() needs to be checked.
> To avoid use of null pointer in case of the failure of alloc.
>
> Fixes: 3d14c5d2b6e1 ("ceph: factor out libceph from Ceph file system")
> Signed-off-by: Jiasheng Jiang <[email protected]>
> ---
> net/ceph/osd_client.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
> index ff8624a7c964..3203e8a34370 100644
> --- a/net/ceph/osd_client.c
> +++ b/net/ceph/osd_client.c
> @@ -1234,6 +1234,8 @@ static struct ceph_osd *create_osd(struct ceph_osd_client *osdc, int onum)
> WARN_ON(onum == CEPH_HOMELESS_OSD);
>
> osd = kzalloc(sizeof(*osd), GFP_NOIO | __GFP_NOFAIL);
> + if (!osd)
> + return NULL;
> osd_init(osd);
> osd->o_osdc = osdc;
> osd->o_osd = onum;

__GFP_NOFAIL should ensure that it never returns NULL, right?

Also, if you're going to fix this up to handle that error then you
probably also need to fix lookup_create_osd to handle a NULL return from
create_osd as well.
--
Jeff Layton <[email protected]>

2021-12-09 12:59:28

by Xiubo Li

Subject: Re: [PATCH] libceph, ceph: potential dereference of null pointer

On 12/9/21 7:20 PM, Jeff Layton wrote:
> On Thu, 2021-12-09 at 10:50 +0800, Jiasheng Jiang wrote:
>> The return value of kzalloc() needs to be checked.
>> To avoid use of null pointer in case of the failure of alloc.
>>
>> Fixes: 3d14c5d2b6e1 ("ceph: factor out libceph from Ceph file system")
>> Signed-off-by: Jiasheng Jiang <[email protected]>
>> ---
>> net/ceph/osd_client.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
>> index ff8624a7c964..3203e8a34370 100644
>> --- a/net/ceph/osd_client.c
>> +++ b/net/ceph/osd_client.c
>> @@ -1234,6 +1234,8 @@ static struct ceph_osd *create_osd(struct ceph_osd_client *osdc, int onum)
>> WARN_ON(onum == CEPH_HOMELESS_OSD);
>>
>> osd = kzalloc(sizeof(*osd), GFP_NOIO | __GFP_NOFAIL);
>> + if (!osd)
>> + return NULL;
>> osd_init(osd);
>> osd->o_osdc = osdc;
>> osd->o_osd = onum;
> __GFP_NOFAIL should ensure that it never returns NULL, right?

Yeah, from the comment, it make no sense to test for failure here:


204? * %__GFP_NOFAIL: The VM implementation _must_ retry infinitely: the
caller
205? * cannot handle allocation failures. The allocation could block
206? * indefinitely but will never return with failure. Testing for
207? * failure is pointless.
208? * New users should be evaluated carefully (and the flag should be
209? * used only when there is no reasonable failure policy) but it is
210? * definitely preferable to use the flag rather than opencode endless
211? * loop around allocator.
212? * Using this flag for costly allocations is _highly_ discouraged.
213? */



> Also, if you're going to fix this up to handle that error then you
> probably also need to fix lookup_create_osd to handle a NULL return from
> create_osd as well.