Re: [PATCH V2 3/3] nvmet-tcp: fix memory leak when performing a controller reset

[Maurizio Lombardi <mlombard@redhat.com>]

On Tue, Nov 16, 2021 at 11:07:29AM +0200, Sagi Grimberg wrote:
> 
> > If a reset controller is executed while the initiator
> > is performing some I/O the driver may leak the memory allocated
> > for the commands' iovec.
> > 
> > Make sure that nvmet_tcp_uninit_data_in_cmds() releases
> > all the memory.
> > 
> > Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
> > ---
> >   drivers/nvme/target/tcp.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/nvme/target/tcp.c b/drivers/nvme/target/tcp.c
> > index 028b47ff0f0f..5a238fa067cd 100644
> > --- a/drivers/nvme/target/tcp.c
> > +++ b/drivers/nvme/target/tcp.c
> > @@ -1427,7 +1427,10 @@ static void nvmet_tcp_uninit_data_in_cmds(struct nvmet_tcp_queue *queue)
> >   	for (i = 0; i < queue->nr_cmds; i++, cmd++) {
> >   		if (nvmet_tcp_need_data_in(cmd))
> > -			nvmet_tcp_finish_cmd(cmd);
> > +			nvmet_req_uninit(&cmd->req);
> > +
> > +		nvmet_tcp_unmap_pdu_iovec(cmd);
> > +		nvmet_tcp_free_iovec(cmd);
> 
> I understand how unmap_pdu_iovec is re-entrance safe, but sgl_free
> called from free_iovec is not. What prevents it from being called
> for commands that have already freed their sgls?

The commands that have already freed their sgls
will have the pointers set to NULL,
calling sgl_free() against a NULL pointer is safe (it does nothing, like kfree())
but if you prefer I will add a check.

Maurizio