CVE-2025-39857

In the Linux kernel, the following vulnerability has been resolved:

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.