netdev - Re: [PATCH net] net/smc: fix one NULL pointer dereference in smc_ib_is_sg_need

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Message-ID: <20250826094138.GA67990@j66a10360.sqa.eu95>
Date: Tue, 26 Aug 2025 17:41:38 +0800
From: "D. Wythe" <alibuda@...ux.alibaba.com    >
To: Liu Jian <liujian56@...wei.com>
Cc: alibuda@...ux.alibaba.com, dust.li@...ux.alibaba.com,
	sidraya@...ux.ibm.com, wenjia@...ux.ibm.com, mjambigi@...ux.ibm.com,
	tonylu@...ux.alibaba.com, guwen@...ux.alibaba.com,
	davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org,
	pabeni@...hat.com, horms@...nel.org,
	guangguan.wang@...ux.alibaba.com, linux-rdma@...r.kernel.org,
	linux-s390@...r.kernel.org, netdev@...r.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?