Re: [PATCH v2] ceph: fix possible NULL pointer dereference for req->r_session

[Xiubo Li <xiubli@redhat.com>]

On 4/18/22 6:43 PM, Aaron Tomlin wrote:
> On Mon 2022-04-18 09:44 +0800, Xiubo Li wrote:
>> The request will be inserted into the ci->i_unsafe_dirops before
>> assigning the req->r_session, so it's possible that we will hit
>> NULL pointer dereference bug here.
>>
>> URL: https://tracker.ceph.com/issues/55327
>> Signed-off-by: Xiubo Li <xiubli@redhat.com>
>> ---
>>   fs/ceph/caps.c | 4 ++++
>>   1 file changed, 4 insertions(+)
>>
>> diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
>> index 69af17df59be..c70fd747c914 100644
>> --- a/fs/ceph/caps.c
>> +++ b/fs/ceph/caps.c
>> @@ -2333,6 +2333,8 @@ static int unsafe_request_wait(struct inode *inode)
>>   			list_for_each_entry(req, &ci->i_unsafe_dirops,
>>   					    r_unsafe_dir_item) {
>>   				s = req->r_session;
>> +				if (!s)
>> +					continue;
>>   				if (unlikely(s->s_mds >= max_sessions)) {
>>   					spin_unlock(&ci->i_unsafe_lock);
>>   					for (i = 0; i < max_sessions; i++) {
>> @@ -2353,6 +2355,8 @@ static int unsafe_request_wait(struct inode *inode)
>>   			list_for_each_entry(req, &ci->i_unsafe_iops,
>>   					    r_unsafe_target_item) {
>>   				s = req->r_session;
>> +				if (!s)
>> +					continue;
>>   				if (unlikely(s->s_mds >= max_sessions)) {
>>   					spin_unlock(&ci->i_unsafe_lock);
>>   					for (i = 0; i < max_sessions; i++) {
>> -- 
>> 2.36.0.rc1
> Tested-by: Aaron Tomlin <atomlin@redhat.com>
>
Hi Aaron,

Thanks very much for you testing.

BTW, did you test this by using Livepatch or something else ?

-- Xiubo