Re: [PATCH] firewire:queue the right number of data
From: JiSheng Zhang
Date: Mon Jul 21 2008 - 02:50:28 EST
on Sun, 20 Jul 2008 16:00:32 +0200
Stefan Richter <stefanr@xxxxxxxxxxxxxxxxx> wrote:
> JiSheng Zhang wrote at LKML:
> > Hi,
> > There will be 4 padding bytes in struct fw_cdev_event_response on some platforms
> > The member:__u32 data will point to these padding bytes. While queue the
> > response and data in complete_transaction in fw-cdev.c, it will queue like this:
> > |response(excluding padding bytes)|4 padding bytes|4 padding bytes|data.
> > It queue 4 extra bytes. That is to say it use "&response + sizeof(response)"
> > while other place of kernel and userspace library use "&response + offsetof
> > (typeof(response), data)". So it will lost the last 4 bytes of data.This patch
> > can fix it while not changing the struct definition.
> > Sorry for open a new ticket.
> > Signed-off-by: JiSheng Zhang <jszhang3@xxxxxxxxxxxxxxxx>
> > --- old/drivers/firewire/fw-cdev.c
> > +++ new/drivers/firewire/fw-cdev.c
> > @@ -382,9 +382,9 @@
> > response->response.type = FW_CDEV_EVENT_RESPONSE;
> > response->response.rcode = rcode;
> > - queue_event(client, &response->event,
> > - &response->response, sizeof(response->response),
> > - response->response.data, response->response.length);
> > + queue_event(client, &response->event, &response->response,
> > + sizeof(response->response) + response->response.length,
> > + NULL, 0);
> > }
> > static int ioctl_send_request(struct client *client, void *buffer)
> I tested it now on i686, x86-64, and x86-64 with i686 userland, using
> firecontrol and gscanbus. As discussed, they got corrupted block read
> responses on x86-64 and on x86-64 with i686 userland. The patch fixes this.
> I committed it to linux1394-2.6.git#fixes and intend to send it upstream
> at the end of the week or so. Thanks for spotting this bug.
Thanks for committing.
> One point about which I am not sure about yet is what happens if there
> are multiple events queued up before the client can read() them. The
> tests which I did so far involved only a single event queued and
> dequeued at a time.
IMHO, even there are multiple events queued, it should work OK because
events are put into event_list rather than a ring buffer, there is no
padding bytes problem between events.
> I removed a rule from linux1394-devel's header filters which matched
> your previous posts. (Message has priority, but no X-Mailer/User-Agent)
Thanks very much
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