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

[Liu Jian <liujian56@huawei.com>]

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;
-- 
2.34.1