linux-kernel - Re: [PATCH] scsi: target: tcm_loop: fix segfault in tcm_loop_tpg_address

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Message-ID: <2c70e9bf-e6fb-4443-bfc9-fab448fb2f65@nvidia.com>
Date: Thu, 6 Nov 2025 06:41:00 +0000
From: Chaitanya Kulkarni <chaitanyak@...dia.com>
To: Hamza Mahfooz <hamzamahfooz@...ux.microsoft.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC: "Martin K. Petersen" <martin.petersen@...cle.com>, Guixin Liu
	<kanie@...ux.alibaba.com>, Nicholas Bellinger <nab@...ux-iscsi.org>, Sheng
 Yang <sheng@...ker.org>, "linux-scsi@...r.kernel.org"
	<linux-scsi@...r.kernel.org>, "target-devel@...r.kernel.org"
	<target-devel@...r.kernel.org>, Allen Pais <apais@...ux.microsoft.com>,
	"stable@...r.kernel.org" <stable@...r.kernel.org>
Subject: Re: [PATCH] scsi: target: tcm_loop: fix segfault in
 tcm_loop_tpg_address_show()

On 11/5/25 11:25, Hamza Mahfooz wrote:
> If the allocation of tl_hba->sh fails in tcm_loop_driver_probe() and we
> attempt to dereference it in tcm_loop_tpg_address_show() we will get a
> segfault, see below for an example. So, check tl_hba->sh before
> dereferencing it.
>
>    Unable to allocate struct scsi_host
>    BUG: kernel NULL pointer dereference, address: 0000000000000194
>    #PF: supervisor read access in kernel mode
>    #PF: error_code(0x0000) - not-present page
>    PGD 0 P4D 0
>    Oops: 0000 [#1] PREEMPT SMP NOPTI
>    CPU: 1 PID: 8356 Comm: tokio-runtime-w Not tainted 6.6.104.2-4.azl3 #1
>    Hardware name: Microsoft Corporation Virtual Machine/Virtual Machine, BIOS Hyper-V UEFI Release v4.1 09/28/2024
>    RIP: 0010:tcm_loop_tpg_address_show+0x2e/0x50 [tcm_loop]
> ...
>    Call Trace:
>     <TASK>
>     configfs_read_iter+0x12d/0x1d0 [configfs]
>     vfs_read+0x1b5/0x300
>     ksys_read+0x6f/0xf0
> ...
>
> Cc:stable@...r.kernel.org
> Fixes: 2628b352c3d4 ("tcm_loop: Show address of tpg in configfs")
> Signed-off-by: Hamza Mahfooz<hamzamahfooz@...ux.microsoft.com>
> ---


indeed :-

  313 static int tcm_loop_driver_probe(struct device *dev)
  314 {
  315         struct tcm_loop_hba *tl_hba;
  316         struct Scsi_Host *sh;
  317         int error, host_prot;
  318
  319         tl_hba = to_tcm_loop_hba(dev);
  320
  321         sh = scsi_host_alloc(&tcm_loop_driver_template,
  322                         sizeof(struct tcm_loop_hba));
  323         if (!sh) {
  324                 pr_err("Unable to allocate struct scsi_host\n");
  325                 return -ENODEV;
  326         }
  327         tl_hba->sh = sh;


Looks good.

Reviewed-by: Chaitanya Kulkarni <kch@...dia.com>

-ck