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

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Commit 27f58c04a8 ("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: 27f58c04a8 ("scsi: sg: Avoid sg device teardown race")
Cc: stable@vger.kernel.org
Signed-off-by: Alexander Wetzel <Alexander@wetzel-home.de>
Link: https://lore.kernel.org/r/20240401191038.18359-1-Alexander@wetzel-home.de
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Alexander Wetzel 2024-04-01 21:10:38 +02:00 • committed by Martin K. Petersen
parent 2a26a11e9c
commit d4e655c49f
1 changed files with 10 additions and 8 deletions
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18
drivers/scsi/sg.c
View file

@ -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 @@ out_undo:
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);