Re:[PATCH] Check sk before sendpage

[<yang.bin18-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org>]

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> On Wed, 2019-07-10 at 17:47 +0000, Lee Duncan wrote:
> > On 7/10/19 12:30 AM, Yang Bin wrote:
> > 
> > > From: " Yang Bin "<yang.bin18-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org>
> > > 
> > > Before xmit,iscsi may disconnect just now.
> > > So must check connection sock NULL or not,or kernel will crash for
> > > accessing NULL pointer.
> > > 
> > > Signed-off-by: Yang Bin <yang.bin18-Th6q7B73Y6EnDS1+zs4M5A@public.gmane.org>
> > > ---
> > >  drivers/scsi/iscsi_tcp.c | 3 +++
> > >  1 file changed, 3 insertions(+)
> > > 
> > > diff --git a/drivers/scsi/iscsi_tcp.c b/drivers/scsi/iscsi_tcp.c
> > > index 7bedbe8..a59c49f 100644
> > > --- a/drivers/scsi/iscsi_tcp.c
> > > +++ b/drivers/scsi/iscsi_tcp.c
> > > @@ -264,6 +264,9 @@ static int iscsi_sw_tcp_xmit_segment(struct
> > > iscsi_tcp_conn *tcp_conn,
> > >      unsigned int copied = 0;
> > >      int r = 0;
> > >  
> > > +    if (!sk)
> > > +        return -ENOTCONN;
> > > +
> > >      while (!iscsi_tcp_segment_done(tcp_conn, segment, 0, r)) {
> > >          struct scatterlist *sg;
> > >          unsigned int offset, copy;
> > > 
> > 
> > If the socket can be closed right before iscsi_sw_tcp_xmit_segment()
> > is called, can it be called in the middle of sending segments? (In
> > which case the check would have to be in the while loop.)

> I think the important point is: is this an actual observed bug or just
> a theoretical problem?

> The reason for asking is this call is controlled directly by the
> ISCSI_UEVENT_DESTROY_CONN event sent by the iscsi daemon.  Obviously if
> the daemon goes haywire and doesn't shut down the connection before
> sending the destroy event, we may get the crash, but I would be
> inclined to say fix the daemon.

> James
We have repproduced this bug several times .
It`s a good idea that sending ISCSI_UEVENT_STOP_CONN event  first.
But there is another choice , adding "iscsi_suspend_tx" int the front of "destroy" ,
for not increasing dependence between kernel and daemon.

 Yangbin

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