Commit d4e655c4 authored by Alexander Wetzel's avatar Alexander Wetzel Committed by Martin K. Petersen
Browse files

scsi: sg: Avoid race in error handling & drop bogus warn 

Commit 27f58c04 ("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().

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: 27f58c04 ("scsi: sg: Avoid sg device teardown race")
Cc: stable@vger.kernel.org
Signed-off-by: default avatarAlexander Wetzel <Alexander@wetzel-home.de>
Link: https://lore.kernel.org/r/20240401191038.18359-1-Alexander@wetzel-home.de


Tested-by: default avatarSachin Sant <sachinp@linux.ibm.com>
Reviewed-by: default avatarBart Van Assche <bvanassche@acm.org>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 2a26a11e

drivers/scsi/sg.c

+10 −8
Original line number Diff line number Diff line
@@ -285,6 +285,7 @@ sg_open(struct inode *inode, struct file *filp) 
	int dev = iminor(inode);

	int flags = filp->f_flags;

	struct request_queue *q;

	struct scsi_device *device;

	Sg_device *sdp;

	Sg_fd *sfp;

	int retval;
@@ -301,11 +302,12 @@ sg_open(struct inode *inode, struct file *filp) 


	/* This driver's module count bumped by fops_get in <linux/fs.h> */

	/* Prevent the device driver from vanishing while we sleep */

	retval = scsi_device_get(sdp->device);

	device = sdp->device;

	retval = scsi_device_get(device);

	if (retval)

		goto sg_put;



	retval = scsi_autopm_get_device(sdp->device);

	retval = scsi_autopm_get_device(device);

	if (retval)

		goto sdp_put;
@@ -313,7 +315,7 @@ sg_open(struct inode *inode, struct file *filp) 
	 * check if O_NONBLOCK. Permits SCSI commands to be issued

	 * during error recovery. Tread carefully. */

	if (!((flags & O_NONBLOCK) ||

	      scsi_block_when_processing_errors(sdp->device))) {

	      scsi_block_when_processing_errors(device))) {

		retval = -ENXIO;

		/* we are in error recovery for this device */

		goto error_out;
@@ -344,7 +346,7 @@ sg_open(struct inode *inode, struct file *filp) 


	if (sdp->open_cnt < 1) {  /* no existing opens */

		sdp->sgdebug = 0;

		q = sdp->device->request_queue;

		q = device->request_queue;

		sdp->sg_tablesize = queue_max_segments(q);

	}

	sfp = sg_add_sfp(sdp);
@@ -370,10 +372,11 @@ sg_open(struct inode *inode, struct file *filp) 
error_mutex_locked:

	mutex_unlock(&sdp->open_rel_lock);

error_out:

	scsi_autopm_put_device(sdp->device);

	scsi_autopm_put_device(device);

sdp_put:

	scsi_device_put(sdp->device);

	goto sg_put;

	kref_put(&sdp->d_ref, sg_device_destroy);

	scsi_device_put(device);

	return retval;

}



/* Release resources associated with a successful sg_open()
@@ -2233,7 +2236,6 @@ sg_remove_sfp_usercontext(struct work_struct *work) 
			"sg_remove_sfp: sfp=0x%p\n", sfp));

	kfree(sfp);



	WARN_ON_ONCE(kref_read(&sdp->d_ref) != 1);

	kref_put(&sdp->d_ref, sg_device_destroy);

	scsi_device_put(device);

	module_put(THIS_MODULE);