From: Bart Van Assche <bvanassche@acm.org>
To: Alexander Wetzel <Alexander@wetzel-home.de>, dgilbert@interlog.com
Cc: gregkh@linuxfoundation.org, sachinp@linux.ibm.com,
linux-scsi@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
martin.petersen@oracle.com, stable@vger.kernel.org
Subject: Re: [PATCH v2] scsi: sg: Avoid race in error handling & drop bogus warn
Date: Mon, 1 Apr 2024 10:09:57 -0700 [thread overview]
Message-ID: <a8b8aabf-250d-46c0-a9b8-fba414e3cfcc@acm.org> (raw)
In-Reply-To: <20240401100317.5395-1-Alexander@wetzel-home.de>
On 4/1/24 03:03, Alexander Wetzel wrote:
> commit 27f58c04a8f4 ("scsi: sg: Avoid sg device teardown race")
> introduced an incorrect WARN_ON_ONCE() and missed a sequence where
> sg_device_destroy() was used after scsi_device_put().
Isn't that too negative? I think that the WARN_ON_ONCE() mentioned above
has proven to be useful: it helped to catch a bug.
> sg_device_destroy() is accessing the parent scsi_device request_queue which
> will already be set to NULL when the preceding call to scsi_device_put()
> removed the last reference to the parent scsi_device.
>
> Drop the incorrect WARN_ON_ONCE() - allowing more than one concurrent
> access to the sg device - and make sure sg_device_destroy() is not used
> after scsi_device_put() in the error handling.
>
> Link: https://lore.kernel.org/all/5375B275-D137-4D5F-BE25-6AF8ACAE41EF@linux.ibm.com
> Fixes: 27f58c04a8f4 ("scsi: sg: Avoid sg device teardown race")
The "goto sg_put" removed by this patch was introduced by commit
cc833acbee9d ("sg: O_EXCL and other lock handling"). Since the latter
commit is older than the one mentioned above, shouldn't the Fixes tag
refer to the latter commit?
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index 386981c6976a..833c9277419b 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -372,8 +372,9 @@ sg_open(struct inode *inode, struct file *filp)
> error_out:
> scsi_autopm_put_device(sdp->device);
> sdp_put:
> + kref_put(&sdp->d_ref, sg_device_destroy);
> scsi_device_put(sdp->device);
> - goto sg_put;
> + return retval;
> }
Please add a comment above "return retval" that explains which code will
drop the sg reference.
Thanks,
Bart.
WARNING: multiple messages have this Message-ID (diff)
From: Bart Van Assche <bvanassche@acm.org>
To: Alexander Wetzel <Alexander@wetzel-home.de>, dgilbert@interlog.com
Cc: martin.petersen@oracle.com, linux-scsi@vger.kernel.org,
gregkh@linuxfoundation.org, stable@vger.kernel.org,
sachinp@linux.ibm.com, linuxppc-dev@lists.ozlabs.org
Subject: Re: [PATCH v2] scsi: sg: Avoid race in error handling & drop bogus warn
Date: Mon, 1 Apr 2024 10:09:57 -0700 [thread overview]
Message-ID: <a8b8aabf-250d-46c0-a9b8-fba414e3cfcc@acm.org> (raw)
In-Reply-To: <20240401100317.5395-1-Alexander@wetzel-home.de>
On 4/1/24 03:03, Alexander Wetzel wrote:
> commit 27f58c04a8f4 ("scsi: sg: Avoid sg device teardown race")
> introduced an incorrect WARN_ON_ONCE() and missed a sequence where
> sg_device_destroy() was used after scsi_device_put().
Isn't that too negative? I think that the WARN_ON_ONCE() mentioned above
has proven to be useful: it helped to catch a bug.
> sg_device_destroy() is accessing the parent scsi_device request_queue which
> will already be set to NULL when the preceding call to scsi_device_put()
> removed the last reference to the parent scsi_device.
>
> Drop the incorrect WARN_ON_ONCE() - allowing more than one concurrent
> access to the sg device - and make sure sg_device_destroy() is not used
> after scsi_device_put() in the error handling.
>
> Link: https://lore.kernel.org/all/5375B275-D137-4D5F-BE25-6AF8ACAE41EF@linux.ibm.com
> Fixes: 27f58c04a8f4 ("scsi: sg: Avoid sg device teardown race")
The "goto sg_put" removed by this patch was introduced by commit
cc833acbee9d ("sg: O_EXCL and other lock handling"). Since the latter
commit is older than the one mentioned above, shouldn't the Fixes tag
refer to the latter commit?
> diff --git a/drivers/scsi/sg.c b/drivers/scsi/sg.c
> index 386981c6976a..833c9277419b 100644
> --- a/drivers/scsi/sg.c
> +++ b/drivers/scsi/sg.c
> @@ -372,8 +372,9 @@ sg_open(struct inode *inode, struct file *filp)
> error_out:
> scsi_autopm_put_device(sdp->device);
> sdp_put:
> + kref_put(&sdp->d_ref, sg_device_destroy);
> scsi_device_put(sdp->device);
> - goto sg_put;
> + return retval;
> }
Please add a comment above "return retval" that explains which code will
drop the sg reference.
Thanks,
Bart.
next prev parent reply other threads:[~2024-04-01 17:10 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-03-29 9:08 [powerpc] WARN at drivers/scsi/sg.c:2236 (sg_remove_sfp_usercontext) Sachin Sant
2024-03-29 9:08 ` Sachin Sant
2024-03-29 11:10 ` Alexander Wetzel
2024-03-29 11:10 ` Alexander Wetzel
2024-03-29 14:37 ` Sachin Sant
2024-04-01 9:56 ` [PATCH] scsi: sg: Avoid race in error handling & drop bogus warn Alexander Wetzel
2024-04-01 9:56 ` Alexander Wetzel
2024-04-01 10:03 ` [PATCH v2] " Alexander Wetzel
2024-04-01 10:03 ` Alexander Wetzel
2024-04-01 17:09 ` Bart Van Assche [this message]
2024-04-01 17:09 ` Bart Van Assche
2024-04-01 19:01 ` Alexander Wetzel
2024-04-01 19:01 ` Alexander Wetzel
2024-04-01 19:10 ` [PATCH v3] " Alexander Wetzel
2024-04-01 19:10 ` Alexander Wetzel
2024-04-02 6:01 ` Sachin Sant
2024-04-02 6:01 ` Sachin Sant
2024-04-03 23:24 ` Bart Van Assche
2024-04-03 23:24 ` Bart Van Assche
2024-04-04 6:55 ` Alexander Wetzel
2024-04-04 6:55 ` Alexander Wetzel
2024-04-04 16:34 ` Bart Van Assche
2024-04-04 16:34 ` Bart Van Assche
2024-04-04 22:22 ` Martin K. Petersen
2024-04-04 22:22 ` Martin K. Petersen
2024-04-06 1:58 ` Martin K. Petersen
2024-04-06 1:58 ` Martin K. Petersen
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