Re: [PATCH bpf-next 7/8] selftests/bpf: Test forbidden bpf_ksock_sendto() LSM attach

[Mahe Tardy <mahe.tardy@gmail.com>]

On Tue, Oct 20, 2026 at 10:52:16AM +0000, bot+bpf-ci@kernel.org wrote:
> > selftests/bpf: Test forbidden bpf_ksock_sendto() LSM attach
> 
> TL;DR:
> - Selftest calls bpf_ksock_sendto() without a prototype until a later patch,
>   so the test may not build or run here (bisectability)
> - Double blank line nit
> 
> > diff --git a/tools/testing/selftests/bpf/progs/ksock_lsm_verifier.c b/tools/testing/selftests/bpf/progs/ksock_lsm_verifier.c
> > --- a/tools/testing/selftests/bpf/progs/ksock_lsm_verifier.c
> > +++ b/tools/testing/selftests/bpf/progs/ksock_lsm_verifier.c
> > @@ -33,7 +33,26 @@ int BPF_PROG(socket_sendmsg_ksock_send, struct socket *sock, struct msghdr *msg,
> >  }
> >
> >  SEC("lsm.s/socket_sendmsg")
> > -__description("bpf_ksock operations other than send are allowed from socket_sendmsg LSM hook")
> > +__description("bpf_ksock_sendto is rejected from socket_sendmsg LSM hook")
> > +__failure __msg("calling kernel function bpf_ksock_sendto is not allowed")
> > +int BPF_PROG(socket_sendmsg_ksock_sendto, struct socket *sock,
> > +	     struct msghdr *msg, int size, int ret)
> > +{
> > +	struct bpf_ksock *ks;
> > +
> > +	ks = ksock_ctx_get();
> > +	if (!ks)
> > +		return ret;
> > +
> > +	bpf_ksock_sendto(ks, send_data, sizeof(send_data), NULL, 0);
> 
> Is there a BPF-side prototype for bpf_ksock_sendto() at this point in the
> series?
> 
> ksock_common.h declares bpf_ksock_create(), bpf_ksock_connect(),
> bpf_ksock_acquire(), bpf_ksock_release() and bpf_ksock_send() with __ksym,
> and this patch only touches progs/ksock_lsm_verifier.c, so nothing declares
> bpf_ksock_sendto().  vmlinux.h carries types only, not function prototypes.
> 
> With a recent clang this should be a call to an undeclared function, which
> is an error.  With an older clang the call would be emitted as an undefined
> external symbol without __ksym/BTF information, and libbpf would fail to
> open or load the object.
> 
> Either way ksock_lsm_verifier.bpf.o, and therefore RUN_TESTS(ksock_lsm_verifier)
> in prog_tests/ksock.c, would not build or run at this commit, which breaks
> bisectability.
> 
> The declaration is only added by the later patch "selftests/bpf: Test ksock
> sendto()" (65327a57ba55), which adds this to ksock_common.h:
> 
>   int bpf_ksock_sendto(struct bpf_ksock *ks, const void *data, u32 data__sz,
>                        const union bpf_ksock_addr *addr__nullable,
>                        u32 addr__sz) __ksym;
> 
> Could that declaration move into this patch, or this patch be reordered after
> that one?

Yeah I re-ordered the last two patches last minute and forgot about
this.

> 
> > +	bpf_ksock_release(ks);
> > +
> > +	return ret;
> > +}
> > +
> > +
> 
> This isn't a bug, but there are two consecutive blank lines here after
> socket_sendmsg_ksock_sendto(), while the other programs in this file are
> separated by a single blank line (checkpatch --strict reports "Please don't
> use multiple blank lines").  Could one of them be dropped?

sure.

> 
> > +SEC("lsm.s/socket_sendmsg")
> > +__description("bpf_ksock acquire and release are allowed from socket_sendmsg LSM hook")
> >  __success
> >  int BPF_PROG(socket_sendmsg_ksock_allowed, struct socket *sock,
> >  	     struct msghdr *msg, int size, int ret)
> 
> [ ... ]
> 
> > @@ -103,6 +122,7 @@ int BPF_PROG(socket_connect_ksock_allowed, struct socket *sock,
> >  		return ret;
> >
> >  	bpf_ksock_send(ks, send_data, sizeof(send_data));
> > +	bpf_ksock_sendto(ks, send_data, sizeof(send_data), NULL, 0);
> 
> This call to bpf_ksock_sendto() has the same missing-prototype problem
> described above.
> 
> >  	bpf_ksock_release(ks);
> >
> >  	return ret;
> 
> 
> ---
> AI reviewed your patch. Please fix the bug or email reply why it's not a bug.
> See: https://github.com/kernel-patches/vmtest/blob/master/ci/claude/README.md
> 
> CI run summary: https://github.com/kernel-patches/bpf/actions/runs/39408886865