On Thursday 06/02 at 15:50 -0700, Calvin Owens wrote: > On 05/13/2016 01:28 PM, Calvin Owens wrote: > > Currently we free the resources backing the enclosure device before we > > call device_unregister(). This is racy: during rmmod of low-level SCSI > > drivers that hook into enclosure, we end up with a small window of time > > during which writing to /sys can OOPS. Example trace with mpt3sas: > > Ping? Any thoughts? Squinting at this more it still seems racy, but a narrow race is surely better than just blatantly freeing everything while the file is still exposed in /sys? Is there a better way you'd prefer I accomplish this? (I have boxes that OOPS all the time from monitoring code reading the /sys files, with this patch I haven't seen a single one.) Thanks, Calvin > > general protection fault: 0000 [#1] SMP KASAN > > Modules linked in: mpt3sas(-) <...> > > RIP: [<ffffffffa0388a98>] ses_get_page2_descriptor.isra.6+0x38/0x220 [ses] > > Call Trace: > > [<ffffffffa0389d14>] ses_set_fault+0xf4/0x400 [ses] > > [<ffffffffa0361069>] set_component_fault+0xa9/0xf0 [enclosure] > > [<ffffffff8205bffc>] dev_attr_store+0x3c/0x70 > > [<ffffffff81677df5>] sysfs_kf_write+0x115/0x180 > > [<ffffffff81675725>] kernfs_fop_write+0x275/0x3a0 > > [<ffffffff8151f810>] __vfs_write+0xe0/0x3e0 > > [<ffffffff8152281f>] vfs_write+0x13f/0x4a0 > > [<ffffffff81526731>] SyS_write+0x111/0x230 > > [<ffffffff828b401b>] entry_SYSCALL_64_fastpath+0x13/0x94 > > > > Fortunately the solution is extremely simple: call device_unregister() > > before we free the resources, and the race no longer exists. The driver > > core holds a reference over ->remove_dev(), so AFAICT this is safe. > > > > Signed-off-by: Calvin Owens <calvinowens@xxxxxx> > > --- > > drivers/scsi/ses.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/scsi/ses.c b/drivers/scsi/ses.c > > index 53ef1cb..0e8601a 100644 > > --- a/drivers/scsi/ses.c > > +++ b/drivers/scsi/ses.c > > @@ -778,6 +778,8 @@ static void ses_intf_remove_enclosure(struct scsi_device *sdev) > > if (!edev) > > return; > > > > + enclosure_unregister(edev); > > + > > ses_dev = edev->scratch; > > edev->scratch = NULL; > > > > @@ -789,7 +791,6 @@ static void ses_intf_remove_enclosure(struct scsi_device *sdev) > > kfree(edev->component[0].scratch); > > > > put_device(&edev->edev); > > - enclosure_unregister(edev); > > } > > > > static void ses_intf_remove(struct device *cdev, > > > -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
