Re: [PATCH] misc: fastrpc: fix potential fastrpc_invoke_ctx leak

[Srinivas Kandagatla]

On 12/05/2020 02:18, Bjorn Andersson wrote:
> On Mon 11 May 09:29 PDT 2020, Srinivas Kandagatla wrote:
>
> > fastrpc_invoke_ctx can have refcount of 2 in error path where
> > rpmsg_send() fails to send invoke message. decrement the refcount
> > properly in the error path to fix this leak.
> >
> > This also fixes below static checker warning:
> >
> > drivers/misc/fastrpc.c:990 fastrpc_internal_invoke()
> > warn: 'ctx->refcount.refcount.ref.counter' not decremented on lines: 990.
> >
> > Fixes: c68cfb718c8f ("misc: fastrpc: Add support for context")
> > Reported-by: Dan Carpenter<dan.carpenter@xxxxxxxxxx>
> > Signed-off-by: Srinivas Kandagatla<srinivas.kandagatla@xxxxxxxxxx>
> > ---
> >   drivers/misc/fastrpc.c | 4 +++-
> >   1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/misc/fastrpc.c b/drivers/misc/fastrpc.c
> > index 9065d3e71ff7..07065728e39f 100644
> > --- a/drivers/misc/fastrpc.c
> > +++ b/drivers/misc/fastrpc.c
> > @@ -949,8 +949,10 @@ static int fastrpc_internal_invoke(struct fastrpc_user *fl,  u32 kernel,
> >   	dma_wmb();
> >   	/* Send invoke buffer to remote dsp */
> >   	err = fastrpc_invoke_send(fl->sctx, ctx, kernel, handle);
> > -	if (err)
> > +	if (err) {
> > +		fastrpc_context_put(ctx);
> So we refcount ctx once for the invoke function and once between send
> and callback. And this fastrpc_context_put() would counter the fact that
> rpmsg_send() failed, so we will not get the "remote's" put().
>
> I think that if you moved this call inside fastrpc_invoke_send() it's
> relationship to the failing rpmsg_send() would be obvious.

That works as well, and sounds much cleaner!


thanks,
srini

> Regards,