[PATCH for 4.4] scsi: core: Remove the /proc/scsi/${proc_name} directory earlier

[PATCH for 4.4] scsi: core: Remove the /proc/scsi/${proc_name} directory earlier

[Nobuhiro Iwamatsu]

From: Bart Van Assche <bvanassche@acm.org>

commit fc663711b94468f4e1427ebe289c9f05669699c9 upstream.

Remove the /proc/scsi/${proc_name} directory earlier to fix a race
condition between unloading and reloading kernel modules. This fixes a bug
introduced in 2009 by commit 77c019768f06 ("[SCSI] fix /proc memory leak in
the SCSI core").

Fix the following kernel warning:

proc_dir_entry 'scsi/scsi_debug' already registered
WARNING: CPU: 19 PID: 27986 at fs/proc/generic.c:376 proc_register+0x27d/0x2e0
Call Trace:
 proc_mkdir+0xb5/0xe0
 scsi_proc_hostdir_add+0xb5/0x170
 scsi_host_alloc+0x683/0x6c0
 sdebug_driver_probe+0x6b/0x2d0 [scsi_debug]
 really_probe+0x159/0x540
 __driver_probe_device+0xdc/0x230
 driver_probe_device+0x4f/0x120
 __device_attach_driver+0xef/0x180
 bus_for_each_drv+0xe5/0x130
 __device_attach+0x127/0x290
 device_initial_probe+0x17/0x20
 bus_probe_device+0x110/0x130
 device_add+0x673/0xc80
 device_register+0x1e/0x30
 sdebug_add_host_helper+0x1a7/0x3b0 [scsi_debug]
 scsi_debug_init+0x64f/0x1000 [scsi_debug]
 do_one_initcall+0xd7/0x470
 do_init_module+0xe7/0x330
 load_module+0x122a/0x12c0
 __do_sys_finit_module+0x124/0x1a0
 __x64_sys_finit_module+0x46/0x50
 do_syscall_64+0x38/0x80
 entry_SYSCALL_64_after_hwframe+0x46/0xb0

Link: https://lore.kernel.org/r/20230210205200.36973-3-bvanassche@acm.org
Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Yi Zhang <yi.zhang@redhat.com>
Cc: stable@vger.kernel.org
Fixes: 77c019768f06 ("[SCSI] fix /proc memory leak in the SCSI core")
Reported-by: Yi Zhang <yi.zhang@redhat.com>
Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Nobuhiro Iwamatsu (CIP) <nobuhiro1.iwamatsu@toshiba.co.jp>
---
 drivers/scsi/hosts.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
index c59b3fd6b361..7ffdebdd9c54 100644
--- a/drivers/scsi/hosts.c
+++ b/drivers/scsi/hosts.c
@@ -173,6 +173,7 @@ void scsi_remove_host(struct Scsi_Host *shost)
 	scsi_forget_host(shost);
 	mutex_unlock(&shost->scan_mutex);
 	scsi_proc_host_rm(shost);
+	scsi_proc_hostdir_rm(shost->hostt);
 
 	spin_lock_irqsave(shost->host_lock, flags);
 	if (scsi_host_set_state(shost, SHOST_DEL))
@@ -322,6 +323,7 @@ static void scsi_host_dev_release(struct device *dev)
 	struct request_queue *q;
 	void *queuedata;
 
+	/* In case scsi_remove_host() has not been called. */
 	scsi_proc_hostdir_rm(shost->hostt);
 
 	if (shost->tmf_work_q)
-- 
2.25.1

Re: [PATCH for 4.4] scsi: core: Remove the /proc/scsi/${proc_name} directory earlier

[Alan Stern]

On Wed, Jun 25, 2025 at 11:00:26AM +0900, Nobuhiro Iwamatsu wrote:
> From: Bart Van Assche <bvanassche@acm.org>
> 
> commit fc663711b94468f4e1427ebe289c9f05669699c9 upstream.
> 
> Remove the /proc/scsi/${proc_name} directory earlier to fix a race
> condition between unloading and reloading kernel modules. This fixes a bug
> introduced in 2009 by commit 77c019768f06 ("[SCSI] fix /proc memory leak in
> the SCSI core").
> 
> Fix the following kernel warning:
> 
> proc_dir_entry 'scsi/scsi_debug' already registered
> WARNING: CPU: 19 PID: 27986 at fs/proc/generic.c:376 proc_register+0x27d/0x2e0
> Call Trace:
>  proc_mkdir+0xb5/0xe0
>  scsi_proc_hostdir_add+0xb5/0x170
>  scsi_host_alloc+0x683/0x6c0
>  sdebug_driver_probe+0x6b/0x2d0 [scsi_debug]
>  really_probe+0x159/0x540
>  __driver_probe_device+0xdc/0x230
>  driver_probe_device+0x4f/0x120
>  __device_attach_driver+0xef/0x180
>  bus_for_each_drv+0xe5/0x130
>  __device_attach+0x127/0x290
>  device_initial_probe+0x17/0x20
>  bus_probe_device+0x110/0x130
>  device_add+0x673/0xc80
>  device_register+0x1e/0x30
>  sdebug_add_host_helper+0x1a7/0x3b0 [scsi_debug]
>  scsi_debug_init+0x64f/0x1000 [scsi_debug]
>  do_one_initcall+0xd7/0x470
>  do_init_module+0xe7/0x330
>  load_module+0x122a/0x12c0
>  __do_sys_finit_module+0x124/0x1a0
>  __x64_sys_finit_module+0x46/0x50
>  do_syscall_64+0x38/0x80
>  entry_SYSCALL_64_after_hwframe+0x46/0xb0

Can you or Bart please explain in more detail the race that causes this 
problem, and add that description to the changelog?  Also, explain how 
this patch fixes the race.

Alan Stern

> Link: https://lore.kernel.org/r/20230210205200.36973-3-bvanassche@acm.org
> Cc: Alan Stern <stern@rowland.harvard.edu>
> Cc: Yi Zhang <yi.zhang@redhat.com>
> Cc: stable@vger.kernel.org
> Fixes: 77c019768f06 ("[SCSI] fix /proc memory leak in the SCSI core")
> Reported-by: Yi Zhang <yi.zhang@redhat.com>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
> Signed-off-by: Nobuhiro Iwamatsu (CIP) <nobuhiro1.iwamatsu@toshiba.co.jp>
> ---
>  drivers/scsi/hosts.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/scsi/hosts.c b/drivers/scsi/hosts.c
> index c59b3fd6b361..7ffdebdd9c54 100644
> --- a/drivers/scsi/hosts.c
> +++ b/drivers/scsi/hosts.c
> @@ -173,6 +173,7 @@ void scsi_remove_host(struct Scsi_Host *shost)
>  	scsi_forget_host(shost);
>  	mutex_unlock(&shost->scan_mutex);
>  	scsi_proc_host_rm(shost);
> +	scsi_proc_hostdir_rm(shost->hostt);
>  
>  	spin_lock_irqsave(shost->host_lock, flags);
>  	if (scsi_host_set_state(shost, SHOST_DEL))
> @@ -322,6 +323,7 @@ static void scsi_host_dev_release(struct device *dev)
>  	struct request_queue *q;
>  	void *queuedata;
>  
> +	/* In case scsi_remove_host() has not been called. */
>  	scsi_proc_hostdir_rm(shost->hostt);
>  
>  	if (shost->tmf_work_q)
> -- 
> 2.25.1
> 
> 

Re: [PATCH for 4.4] scsi: core: Remove the /proc/scsi/${proc_name} directory earlier

[Greg KH]

On Wed, Jun 25, 2025 at 11:00:26AM +0900, Nobuhiro Iwamatsu wrote:
> From: Bart Van Assche <bvanassche@acm.org>
> 
> commit fc663711b94468f4e1427ebe289c9f05669699c9 upstream.

4.4.y is long out-of-support by us, and this is in all activly supported
kenrnels at this time, so why is this sent to us?

confused,

greg k-h

RE: [PATCH for 4.4] scsi: core: Remove the /proc/scsi/${proc_name} directory earlier

[nobuhiro1.iwamatsu]

> -----Original Message-----
> From: Greg KH <gregkh@linuxfoundation.org>
> Sent: Wednesday, June 25, 2025 4:05 PM
> To: iwamatsu nobuhiro(岩松 信洋 □ＤＩＴＣ○ＣＰＴ)
> <nobuhiro1.iwamatsu@toshiba.co.jp>
> Cc: cip-dev@lists.cip-project.org; Ulrich Hecht <uli@fpond.eu>; Pavel
> Machek <pavel@denx.de>; Bart Van Assche <bvanassche@acm.org>; Alan
> Stern <stern@rowland.harvard.edu>; Yi Zhang <yi.zhang@redhat.com>;
> stable@vger.kernel.org; Martin K . Petersen <martin.petersen@oracle.com>
> Subject: Re: [PATCH for 4.4] scsi: core: Remove the /proc/scsi/${proc_name}
> directory earlier
> 
> On Wed, Jun 25, 2025 at 11:00:26AM +0900, Nobuhiro Iwamatsu wrote:
> > From: Bart Van Assche <bvanassche@acm.org>
> >
> > commit fc663711b94468f4e1427ebe289c9f05669699c9 upstream.
> 
> 4.4.y is long out-of-support by us, and this is in all activly supported kenrnels at
> this time, so why is this sent to us?
> 

This was also sent to stable due to the processing of the patch's CC tag.
I'm sorry for the confusion.

Best regards,
  Nobuhiro

Re: [PATCH for 4.4] scsi: core: Remove the /proc/scsi/${proc_name} directory earlier

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
⚠️ Found follow-up fixes in mainline

The upstream commit SHA1 provided is correct: fc663711b94468f4e1427ebe289c9f05669699c9

WARNING: Author mismatch between patch and upstream commit:
Backport author: Nobuhiro Iwamatsu<nobuhiro1.iwamatsu@toshiba.co.jp>
Commit author: Bart Van Assche<bvanassche@acm.org>

Found fixes commits:
be03df3d4bfe scsi: core: Fix a procfs host directory removal regression

Note: The patch differs from the upstream commit:
---
1:  fc663711b9446 < -:  ------------- scsi: core: Remove the /proc/scsi/${proc_name} directory earlier
-:  ------------- > 1:  a2b47f77e740a Linux 6.15.3
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.15.y       |  Success    |  Success   |
| stable/linux-6.12.y       |  Success    |  Success   |
| stable/linux-6.6.y        |  Success    |  Success   |
| stable/linux-6.1.y        |  Success    |  Success   |
| stable/linux-5.15.y       |  Success    |  Success   |
| stable/linux-5.10.y       |  Success    |  Success   |
| stable/linux-5.4.y        |  Success    |  Success   |