Re: [PATCH net-next 3/4] net/smc: fix one NULL pointer dereference in smc_ib_is_sg_need_sync()

["D. Wythe" <alibuda@linux.alibaba.com>]

On 8/9/24 4:31 PM, Liu Jian wrote:
> BUG: kernel NULL pointer dereference, address: 0000000000000238
> PGD 0 P4D 0
> Oops: 0000 [#1] PREEMPT SMP PTI
> CPU: 3 PID: 289 Comm: kworker/3:1 Kdump: loaded Tainted: G           OE
> Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.15.0-1 04/01/2014
> Workqueue: smc_hs_wq smc_listen_work [smc]
> RIP: 0010:dma_need_sync+0x5/0x60
> ...
> Call Trace:
>   <TASK>
>   ? dma_need_sync+0x5/0x60
>   ? smc_ib_is_sg_need_sync+0x61/0xf0 [smc]
>   smcr_buf_map_link+0x24a/0x380 [smc]
>   __smc_buf_create+0x483/0xb10 [smc]
>   smc_buf_create+0x21/0xe0 [smc]
>   smc_listen_work+0xf11/0x14f0 [smc]
>   ? smc_tcp_listen_work+0x364/0x520 [smc]
>   process_one_work+0x18d/0x3f0
>   worker_thread+0x304/0x440
>   kthread+0xe4/0x110
>   ret_from_fork+0x47/0x70
>   ret_from_fork_asm+0x1a/0x30
>   </TASK>
>
> If the software RoCE device is used, ibdev->dma_device is a null pointer.
> As a result, the problem occurs. Null pointer detection is added to
> prevent problems.
>
> Signed-off-by: Liu Jian <liujian56@huawei.com>
> ---
>   net/smc/smc_ib.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/net/smc/smc_ib.c b/net/smc/smc_ib.c
> index 382351ac9434..059822cc3fde 100644
> --- a/net/smc/smc_ib.c
> +++ b/net/smc/smc_ib.c
> @@ -748,6 +748,8 @@ bool smc_ib_is_sg_need_sync(struct smc_link *lnk,
>   		    buf_slot->sgt[lnk->link_idx].nents, i) {
>   		if (!sg_dma_len(sg))
>   			break;
> +		if (!lnk->smcibdev->ibdev->dma_device)
> +			break;
>   		if (dma_need_sync(lnk->smcibdev->ibdev->dma_device,
>   				  sg_dma_address(sg))) {
>   			ret = true;

Maybe you need add a fix tag ?