Re: [PATCH] RDMA/rxe: fix null deref on srq->rq.queue after resize failure

["yanjun.zhu" <yanjun.zhu@linux.dev>]

On 10/21/25 6:42 AM, Junxian Huang wrote:
> 
> 
> On 2025/10/21 10:20, Yi Liu wrote:
>> A NULL pointer dereference can occur in rxe_srq_chk_attr() when
>> ibv_modify_srq() is invoked twice in succession under certain error
>> conditions. The first call may fail in rxe_queue_resize(), which leads
>> rxe_srq_from_attr() to set srq->rq.queue = NULL. The second call then
>> triggers a crash (null deref) when accessing
>> srq->rq.queue->buf->index_mask.
>>
>> Call Trace:
>> <TASK>
>> rxe_modify_srq+0x170/0x480 [rdma_rxe]
>> ? __pfx_rxe_modify_srq+0x10/0x10 [rdma_rxe]
>> ? uverbs_try_lock_object+0x4f/0xa0 [ib_uverbs]
>> ? rdma_lookup_get_uobject+0x1f0/0x380 [ib_uverbs]
>> ib_uverbs_modify_srq+0x204/0x290 [ib_uverbs]
>> ? __pfx_ib_uverbs_modify_srq+0x10/0x10 [ib_uverbs]
>> ? tryinc_node_nr_active+0xe6/0x150
>> ? uverbs_fill_udata+0xed/0x4f0 [ib_uverbs]
>> ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0x2c0/0x470 [ib_uverbs]
>> ? __pfx_ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0x10/0x10 [ib_uverbs]
>> ? uverbs_fill_udata+0xed/0x4f0 [ib_uverbs]
>> ib_uverbs_run_method+0x55a/0x6e0 [ib_uverbs]
>> ? __pfx_ib_uverbs_handler_UVERBS_METHOD_INVOKE_WRITE+0x10/0x10 [ib_uverbs]
>> ib_uverbs_cmd_verbs+0x54d/0x800 [ib_uverbs]
>> ? __pfx_ib_uverbs_cmd_verbs+0x10/0x10 [ib_uverbs]
>> ? __pfx___raw_spin_lock_irqsave+0x10/0x10
>> ? __pfx_do_vfs_ioctl+0x10/0x10
>> ? ioctl_has_perm.constprop.0.isra.0+0x2c7/0x4c0
>> ? __pfx_ioctl_has_perm.constprop.0.isra.0+0x10/0x10
>> ib_uverbs_ioctl+0x13e/0x220 [ib_uverbs]
>> ? __pfx_ib_uverbs_ioctl+0x10/0x10 [ib_uverbs]
>> __x64_sys_ioctl+0x138/0x1c0
>> do_syscall_64+0x82/0x250
>> ? fdget_pos+0x58/0x4c0
>> ? ksys_write+0xf3/0x1c0
>> ? __pfx_ksys_write+0x10/0x10
>> ? do_syscall_64+0xc8/0x250
>> ? __pfx_vm_mmap_pgoff+0x10/0x10
>> ? fget+0x173/0x230
>> ? fput+0x2a/0x80
>> ? ksys_mmap_pgoff+0x224/0x4c0
>> ? do_syscall_64+0xc8/0x250
>> ? do_user_addr_fault+0x37b/0xfe0
>> ? clear_bhb_loop+0x50/0xa0
>> ? clear_bhb_loop+0x50/0xa0
>> ? clear_bhb_loop+0x50/0xa0
>> entry_SYSCALL_64_after_hwframe+0x76/0x7e
>>
>> Fix by aligning the error handling path in rxe_srq_from_attr() with
>> rxe_cq_resize_queue(), which also uses rxe_queue_resize(): do not
>> nullify the queue when resize fails.
>>
>> Reported-by: Liu Yi <asatsuyu.liu@gmail.com>
>> Link: https://paste.ubuntu.com/p/Zhj65q6gr9/
>> Fixes: 8700e3e7c485 ("Soft RoCE driver")
>> Tested-by: Zhu Yanjun <yanjun.zhu@linux.dev>
>> Signed-off-by: Zhu Yanjun <yanjun.zhu@linux.dev>
>> ---
>> drivers/infiniband/sw/rxe/rxe_srq.c | 2 --
>> 1 file changed, 2 deletions(-)
>>
>> diff --git a/drivers/infiniband/sw/rxe/rxe_srq.c
>> b/drivers/infiniband/sw/rxe/rxe_srq.c
>> index 3661cb627d28..2764dc00e2f3 100644
>> --- a/drivers/infiniband/sw/rxe/rxe_srq.c
>> +++ b/drivers/infiniband/sw/rxe/rxe_srq.c
>> @@ -182,8 +182,6 @@ int rxe_srq_from_attr(struct rxe_dev *rxe, struct
>> rxe_srq *srq,
>> return 0;
>>
>> err_free:
>> - rxe_queue_cleanup(q);
>> - srq->rq.queue = NULL;
>> return err;
> 
> A minor suggestion, this err_free label doesn’t seem necessary any more.
> You can return directly at the place where you jump to err_free currently.

Thanks a lot. It might be better to return immediately when an error 
occurs, but keeping the current state unchanged could also be a valid 
option.

Best Regards,
Yanjun.Zhu

> 
> Junxian
> 
>> }
>>
>> --
>> 2.34.1
>>