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Tue, 17 Mar 2026 09:13:42 -0700 (PDT) Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=UTF-8 Date: Tue, 17 Mar 2026 12:13:41 -0400 Message-Id: Subject: Re: [PATCH bpf-next v1 4/4] selftests/bpf: Test modified syscall ctx for global subprog From: "Emil Tsalapatis" To: "Kumar Kartikeya Dwivedi" , Cc: "Alexei Starovoitov" , "Andrii Nakryiko" , "Daniel Borkmann" , "Martin KaFai Lau" , "Eduard Zingerman" , "Tejun Heo" , "Dan Schatzberg" , , X-Mailer: aerc 0.20.1 References: <20260317111850.2107846-1-memxor@gmail.com> <20260317111850.2107846-5-memxor@gmail.com> In-Reply-To: <20260317111850.2107846-5-memxor@gmail.com> On Tue Mar 17, 2026 at 7:18 AM EDT, Kumar Kartikeya Dwivedi wrote: > Ensure that global subprogs can only accept an unmodified PTR_TO_CTX for > syscall programs. For all other program types, fixed or variable offsets > on PTR_TO_CTX is rejected when passed into an argument of any call > instruction type, through the unified logic of check_func_arg_reg_off. > > Finally, add a positive example of a case that should succeed with all > our previous changes. > > Signed-off-by: Kumar Kartikeya Dwivedi > --- Reviewed-by: Emil Tsalapatis > .../bpf/progs/verifier_global_subprogs.c | 42 +++++++++++++++++++ > 1 file changed, 42 insertions(+) > > diff --git a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c= b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c > index 2250fc31574d..0c14adaddb90 100644 > --- a/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c > +++ b/tools/testing/selftests/bpf/progs/verifier_global_subprogs.c > @@ -357,6 +357,48 @@ int arg_tag_ctx_syscall(void *ctx) > return tracing_subprog_void(ctx) + tracing_subprog_u64(ctx) + tp_whatev= er(ctx); > } > =20 > +__weak int syscall_array_bpf_for(void *ctx __arg_ctx) > +{ > + int *arr =3D ctx; > + int i; > + > + bpf_for(i, 0, 100) > + arr[i] *=3D i; > + > + return 0; > +} > + > +SEC("?syscall") > +__success __log_level(2) > +int arg_tag_ctx_syscall_bpf_for(void *ctx) > +{ > + return syscall_array_bpf_for(ctx); > +} > + > +SEC("?syscall") > +__failure __log_level(2) > +__msg("arg#0 of syscall prog must have zero offset") > +int arg_tag_ctx_syscall_fixed_off_bad(void *ctx) > +{ > + char *p =3D ctx; > + > + p +=3D 8; > + return subprog_ctx_tag(p); > +} > + > +SEC("?syscall") > +__failure __log_level(2) > +__msg("arg#0 of syscall prog must have zero offset") > +int arg_tag_ctx_syscall_var_off_bad(void *ctx) > +{ > + __u64 off =3D bpf_get_prandom_u32(); > + char *p =3D ctx; > + > + off &=3D 4; > + p +=3D off; > + return subprog_ctx_tag(p); > +} > + > __weak int subprog_dynptr(struct bpf_dynptr *dptr) > { > long *d, t, buf[1] =3D {};