Re: [PATCH 1/1] Drivers: scsi: storvsc: Account for in-transitpackets in the RESET path
From: James Bottomley
Date: Tue Oct 09 2012 - 07:38:19 EST
On Mon, 2012-10-08 at 15:51 +0000, KY Srinivasan wrote:
>
> > -----Original Message-----
> > From: K. Y. Srinivasan [mailto:kys@xxxxxxxxxxxxx]
> > Sent: Tuesday, October 02, 2012 2:04 PM
> > To: gregkh@xxxxxxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx;
> > devel@xxxxxxxxxxxxxxxxxxxxxx; ohering@xxxxxxxx; jbottomley@xxxxxxxxxxxxx;
> > hch@xxxxxxxxxxxxx; linux-scsi@xxxxxxxxxxxxxxx
> > Cc: KY Srinivasan; stable@xxxxxxxxxxxxxxx
> > Subject: [PATCH 1/1] Drivers: scsi: storvsc: Account for in-transit packets in the
> > RESET path
> >
> > Properly account for I/O in transit before returning from the RESET call.
> > In the absense of this patch, we could have a situation where the host may
> > respond to a command that was issued prior to the issuance of the RESET
> > command at some arbitrary time after responding to the RESET command.
> > Currently, the host does not do anything with the RESET command.
> >
> > Signed-off-by: K. Y. Srinivasan <kys@xxxxxxxxxxxxx>
> > Cc: stable@xxxxxxxxxxxxxxx
> > ---
> > drivers/scsi/storvsc_drv.c | 5 +++++
> > 1 files changed, 5 insertions(+), 0 deletions(-)
> >
> > diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c
> > index 528d52b..0144078 100644
> > --- a/drivers/scsi/storvsc_drv.c
> > +++ b/drivers/scsi/storvsc_drv.c
> > @@ -1221,7 +1221,12 @@ static int storvsc_host_reset_handler(struct scsi_cmnd
> > *scmnd)
> > /*
> > * At this point, all outstanding requests in the adapter
> > * should have been flushed out and return to us
> > + * There is a potential race here where the host may be in
> > + * the process of responding when we return from here.
> > + * Just wait for all in-transit packets to be accounted for
> > + * before we return from here.
> > */
> > + storvsc_wait_to_drain(stor_device);
> >
> > return SUCCESS;
> > }
> > --
> > 1.7.4.1
>
> James,
>
> This patch is critical for running Linux based workloads on our Cloud infrastructure - Azure.
> Please let me know if there are any issues.
So just for next time: it's a bit hard to work out this is a critical
issue from the change log. If I had to guess, I'd say the response to a
command killed by reset causes some type of use after free and a
potential oops (all of which would have been very nice in the change
log)?
James
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