[PATCH net] net/smc: fix one NULL pointer dereference in smc_ib_is_sg_need_sync()

[PATCH net] net/smc: fix one NULL pointer dereference in smc_ib_is_sg_need_sync()

[Liu Jian]

BUG: kernel NULL pointer dereference, address: 00000000000002ec
PGD 0 P4D 0
Oops: Oops: 0000 [#1] SMP PTI
CPU: 28 UID: 0 PID: 343 Comm: kworker/28:1 Kdump: loaded Tainted: G        OE       6.17.0-rc2+ #9 NONE
Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
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:smc_ib_is_sg_need_sync+0x9e/0xd0 [smc]
...
Call Trace:
 <TASK>
 smcr_buf_map_link+0x211/0x2a0 [smc]
 __smc_buf_create+0x522/0x970 [smc]
 smc_buf_create+0x3a/0x110 [smc]
 smc_find_rdma_v2_device_serv+0x18f/0x240 [smc]
 ? smc_vlan_by_tcpsk+0x7e/0xe0 [smc]
 smc_listen_find_device+0x1dd/0x2b0 [smc]
 smc_listen_work+0x30f/0x580 [smc]
 process_one_work+0x18c/0x340
 worker_thread+0x242/0x360
 kthread+0xe7/0x220
 ret_from_fork+0x13a/0x160
 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.

Fixes: 0ef69e788411c ("net/smc: optimize for smc_sndbuf_sync_sg_for_device and smc_rmb_sync_sg_for_cpu")
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 53828833a3f7..85501d2c1f1b 100644
--- a/net/smc/smc_ib.c
+++ b/net/smc/smc_ib.c
@@ -747,6 +747,8 @@ 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

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

[D. Wythe]

On Tue, Aug 26, 2025 at 04:44:42PM +0800, Liu Jian wrote:
> BUG: kernel NULL pointer dereference, address: 00000000000002ec
> PGD 0 P4D 0
> Oops: Oops: 0000 [#1] SMP PTI
> CPU: 28 UID: 0 PID: 343 Comm: kworker/28:1 Kdump: loaded Tainted: G        OE       6.17.0-rc2+ #9 NONE
> Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE
> 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:smc_ib_is_sg_need_sync+0x9e/0xd0 [smc]
> 
> diff --git a/net/smc/smc_ib.c b/net/smc/smc_ib.c
> index 53828833a3f7..85501d2c1f1b 100644
> --- a/net/smc/smc_ib.c
> +++ b/net/smc/smc_ib.c
> @@ -747,6 +747,8 @@ 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;

Why check it inside the loop?

RE: [PATCH net] net/smc: fix one NULL pointer dereference in smc_ib_is_sg_need_sync()

[liujian (CE)]

> -----Original Message-----
> From: D. Wythe [mailto:alibuda@linux.alibaba.com]
> Sent: Tuesday, August 26, 2025 5:42 PM
> To: liujian (CE) <liujian56@huawei.com>
> Cc: alibuda@linux.alibaba.com; dust.li@linux.alibaba.com;
> sidraya@linux.ibm.com; wenjia@linux.ibm.com; mjambigi@linux.ibm.com;
> tonylu@linux.alibaba.com; guwen@linux.alibaba.com;
> davem@davemloft.net; edumazet@google.com; kuba@kernel.org;
> pabeni@redhat.com; horms@kernel.org;
> guangguan.wang@linux.alibaba.com; linux-rdma@vger.kernel.org; linux-
> s390@vger.kernel.org; netdev@vger.kernel.org
> Subject: Re: [PATCH net] net/smc: fix one NULL pointer dereference in
> smc_ib_is_sg_need_sync()
> 
> On Tue, Aug 26, 2025 at 04:44:42PM +0800, Liu Jian wrote:
> > BUG: kernel NULL pointer dereference, address: 00000000000002ec PGD 0
> > P4D 0
> > Oops: Oops: 0000 [#1] SMP PTI
> > CPU: 28 UID: 0 PID: 343 Comm: kworker/28:1 Kdump: loaded Tainted: G
> OE       6.17.0-rc2+ #9 NONE
> > Tainted: [O]=OOT_MODULE, [E]=UNSIGNED_MODULE 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:smc_ib_is_sg_need_sync+0x9e/0xd0 [smc]
> >
> > diff --git a/net/smc/smc_ib.c b/net/smc/smc_ib.c index
> > 53828833a3f7..85501d2c1f1b 100644
> > --- a/net/smc/smc_ib.c
> > +++ b/net/smc/smc_ib.c
> > @@ -747,6 +747,8 @@ 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;
> 
> Why check it inside the loop?
Ok, will send v2, move the check outside of loop.
Thanks.