Re: [dpdk-dev] [PATCH] bpf: fix to allow ptr stack program type

[Jerin Jacob Kollanukkaran <jerinj@marvell.com>]

> -----Original Message-----
> From: Ananyev, Konstantin <konstantin.ananyev@intel.com>
> Sent: Monday, August 12, 2019 2:20 PM
> To: Jerin Jacob Kollanukkaran <jerinj@marvell.com>; dev@dpdk.org
> Cc: thomas@monjalon.net; stable@dpdk.org
> Subject: [EXT] RE: [dpdk-dev] [PATCH] bpf: fix to allow ptr stack program
> type
> 
> ----------------------------------------------------------------------
> Hi Jerin,

Hi Konstantin,

> 
> >
> > bpf_validate does not allow to execute RTE_BPF_ARG_PTR_STACK for no
> > reason.
> 
> I believe there is a reason,
> ARG_PTR_STACK is reserved for memory within BPF program internal stack
> only.
> User that calls BPF program should never pass parameter with that type.

OK.
Shouldn't we remove that from public header file
(lib/librte_bpf/rte_bpf.h) then ?

> If the user allocates parameter for bpf function on the stack, he can still use
> RTE_BPF_ARG_PTR for it.

I see the _stack_ is only allocated under RTE_BPF_ARG_PTR_STACK checks in bpf_validate.c.
Can you check? I agree that stack should be allocated for RTE_BPF_ARG_PTR as well.

I am writing the arm64 JIT support now, I see always stack of size of 0. I did not spend  much
Time on the generic piece of ebpf code(Focusing only on JIT side now).

Can you share more detail the stack allocation scheme, Is validate code parse the eBPF opcode and
Figure out the stack depth it by its own and pass to JIT function where Arch code can allocate
enough stack.



> Konstantin



> 
> > Fix it by enhancing the prog_arg.type check.
> >
> > Fixes: 6e12ec4c4d6d ("bpf: add more checks")
> > Cc: stable@dpdk.org
> >
> > Signed-off-by: Jerin Jacob <jerinj@marvell.com>
> > ---
> >  lib/librte_bpf/bpf_validate.c | 1 +
> >  1 file changed, 1 insertion(+)
> >
> > diff --git a/lib/librte_bpf/bpf_validate.c
> > b/lib/librte_bpf/bpf_validate.c index 0cf41fa27..c75777b6d 100644
> > --- a/lib/librte_bpf/bpf_validate.c
> > +++ b/lib/librte_bpf/bpf_validate.c
> > @@ -2216,6 +2216,7 @@ bpf_validate(struct rte_bpf *bpf)
> >
> >  	/* check input argument type, don't allow mbuf ptr on 32-bit */
> >  	if (bpf->prm.prog_arg.type != RTE_BPF_ARG_RAW &&
> > +			bpf->prm.prog_arg.type !=
> RTE_BPF_ARG_PTR_STACK &&
> >  			bpf->prm.prog_arg.type != RTE_BPF_ARG_PTR &&
> >  			(sizeof(uint64_t) != sizeof(uintptr_t) ||
> >  			bpf->prm.prog_arg.type !=
> RTE_BPF_ARG_PTR_MBUF)) {
> > --
> > 2.22.0