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

From: Dust Li <[email-masked]>
Date: Fri, 9 Aug 2024 22:59:44 +0800

On 2024-08-09 16:31:47, 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 <[email-masked]>

Reviewed-by: Dust Li <[email-masked]>

Best regard,
Dust

>---
> 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;
>-- 
>2.34.1
>