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[192.26.29.3]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-48448e72df2sm15057192f8f.1.2026.09.03.07.44.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Sep 2026 07:44:47 -0700 (PDT) From: Kumar Kartikeya Dwivedi To: bpf@vger.kernel.org Cc: Nicholas Carlini , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Eduard Zingerman , Emil Tsalapatis , kkd@meta.com, kernel-team@meta.com Subject: [PATCH bpf v1 07/10] bpf: Mark sched_process_wait argument as nullable Date: Thu, 3 Sep 2026 16:44:25 +0200 Message-ID: <20260903144433.1716731-8-memxor@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260903144433.1716731-1-memxor@gmail.com> References: <20260903144433.1716731-1-memxor@gmail.com> Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=1523; i=memxor@gmail.com; h=from:subject; bh=N8vxHa417heLzyAHn5WFdm9t8sqkhfIH7fFya7kODho=; b=owGbwMvMwCXmrmtenRyi38x4Wi2JIWtm88Qpe68Xi1mvvxu0Z+Us4ZIT5qc+uU8M8VrQaKbka P93/yzPjlIWBjEuBlkxRZaS//uYjE9U/g60XcYNM4eVCWQIAxenAEzELZOR4UTvTO8D957siM9w PNL/cLeQe2rLxD9T+4WZ9A/KvjFPymZkeHLwz8m7CY9V/oubfL44fU3e2+bse3NNDAMVzspsulT vzgQA X-Developer-Key: i=memxor@gmail.com; a=openpgp; fpr=B34BD741DE8494B76E2F717880EF20021D46C59B Content-Transfer-Encoding: 8bit do_wait() passes wo->wo_pid to the sched_process_wait tracepoint. kernel_wait4() leaves wo_pid NULL for wait4(-1), and kernel_waitid_prepare() does likewise for waitid(P_ALL). btf_ctx_access() currently types argument 0 as PTR_TO_BTF_ID | PTR_TRUSTED. Without PTR_MAYBE_NULL, the verifier accepts an unchecked dereference. Trusted pointer loads have no fault protection, so a wait for any child can then cause a NULL pointer dereference in JITed BPF code. Add sched_process_wait to raw_tp_null_args[] with argument 0 marked nullable. The verifier rejects an unchecked dereference while preserving access after the program checks the pointer for NULL. Fixes: 838a10bd2ebf ("bpf: Augment raw_tp arguments with PTR_MAYBE_NULL") Reported-by: Nicholas Carlini Suggested-by: Nicholas Carlini Signed-off-by: Kumar Kartikeya Dwivedi --- kernel/bpf/btf.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/bpf/btf.c b/kernel/bpf/btf.c index d6d243c262ea..41764356d2d3 100644 --- a/kernel/bpf/btf.c +++ b/kernel/bpf/btf.c @@ -6657,6 +6657,10 @@ struct bpf_raw_tp_null_args { static const struct bpf_raw_tp_null_args raw_tp_null_args[] = { /* sched */ { "sched_pi_setprio", 0x10 }, + /* + * do_wait() passes NULL for wait4(-1) and waitid(P_ALL). + */ + { "sched_process_wait", 0x1 }, /* ... from sched_numa_pair_template event class */ { "sched_stick_numa", 0x100 }, { "sched_swap_numa", 0x100 }, -- 2.53.0