> -----Original Message----- > From: Vitaly Kuznetsov [mailto:vkuznets@xxxxxxxxxx] > Sent: Friday, November 6, 2015 7:49 AM > To: James E.J. Bottomley <JBottomley@xxxxxxxx> > Cc: linux-scsi@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; KY Srinivasan > <kys@xxxxxxxxxxxxx>; Bart Van Assche <bart.vanassche@xxxxxxxxxxx> > Subject: [PATCH RESEND] scsi_sysfs: protect against double execution of > __scsi_remove_device() > > On some host errors storvsc module tries to remove sdev by scheduling a job > which does the following: > > sdev = scsi_device_lookup(wrk->host, 0, 0, wrk->lun); > if (sdev) { > scsi_remove_device(sdev); > scsi_device_put(sdev); > } > > While this code seems correct the following crash is observed: > > general protection fault: 0000 [#1] SMP DEBUG_PAGEALLOC > RIP: 0010:[<ffffffff81169979>] [<ffffffff81169979>] bdi_destroy+0x39/0x220 > ... > [<ffffffff814aecdc>] ? _raw_spin_unlock_irq+0x2c/0x40 > [<ffffffff8127b7db>] blk_cleanup_queue+0x17b/0x270 > [<ffffffffa00b54c4>] __scsi_remove_device+0x54/0xd0 [scsi_mod] > [<ffffffffa00b556b>] scsi_remove_device+0x2b/0x40 [scsi_mod] > [<ffffffffa00ec47d>] storvsc_remove_lun+0x3d/0x60 [hv_storvsc] > [<ffffffff81080791>] process_one_work+0x1b1/0x530 > ... > > The problem comes with the fact that many such jobs (for the same device) > are being scheduled simultaneously. While scsi_remove_device() uses > shost->scan_mutex and scsi_device_lookup() will fail for a device in > SDEV_DEL state there is no protection against someone who did > scsi_device_lookup() before we actually entered __scsi_remove_device(). > So > the whole scenario looks like that: two callers do simultaneous (or > preemption happens) calls to scsi_device_lookup() ant these calls succeed > for both of them, after that they try doing scsi_remove_device(). > shost->scan_mutex only serializes their calls to __scsi_remove_device() > and we end up doing the cleanup path twice. > > Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> James, I too have a bunch of patches in your queue (sent about a month ago). Should I resend them as well. Regards, K. Y -- 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
