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

JIRA: https://issues.redhat.com/browse/RHEL-99998

commit ba1e942
Author: Liu Jian <[email protected]>
Date:   Thu Aug 28 20:41:17 2025 +0800

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

    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: 0ef69e7 ("net/smc: optimize for smc_sndbuf_sync_sg_for_device and smc_rmb_sync_sg_for_cpu")
    Signed-off-by: Liu Jian <[email protected]>
    Reviewed-by: Guangguan Wang <[email protected]>
    Reviewed-by: Zhu Yanjun <[email protected]>
    Reviewed-by: D. Wythe <[email protected]>
    Link: https://patch.msgid.link/[email protected]
    Signed-off-by: Paolo Abeni <[email protected]>

Signed-off-by: Mete Durlu <[email protected]>

Author: Mete Durlu

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) {