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.c... 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.