On 8/28/25 5:41 AM, 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] ... 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.
Normally, SoftRoCE relies on the DMA capabilities of the underlying NIC device. In SMC, if DMA will play an important role in the subsequent operations, we can leverage the NIC device’s DMA.
If DMA is not required for the upcoming actions, then this kind of checking is sufficient.
Reviewed-by: Zhu Yanjun <yanjun.zhu@xxxxxxxxx> Zhu Yanjun
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@xxxxxxxxxx> --- v1->v2: move the check outside of loop. net/smc/smc_ib.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/net/smc/smc_ib.c b/net/smc/smc_ib.c index 53828833a3f7..a42ef3f77b96 100644 --- a/net/smc/smc_ib.c +++ b/net/smc/smc_ib.c @@ -742,6 +742,9 @@ bool smc_ib_is_sg_need_sync(struct smc_link *lnk, unsigned int i; bool ret = false;+ if (!lnk->smcibdev->ibdev->dma_device)+ return ret; + /* for now there is just one DMA address */ for_each_sg(buf_slot->sgt[lnk->link_idx].sgl, sg, buf_slot->sgt[lnk->link_idx].nents, i) {
