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Wed, 01 Apr 2026 12:11:37 -0700 (PDT) Received: from computer.goose-salary.ts.net ([2a09:bac5:40b2:1a96::2a6:7a]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-2b27477c54bsm6805875ad.27.2026.04.01.12.11.31 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 01 Apr 2026 12:11:36 -0700 (PDT) From: Varun R Mallya To: bpf@vger.kernel.org Cc: ast@kernel.org, daniel@iogearbox.net, memxor@gmail.com, yonghong.song@linux.dev, jolsa@kernel.org, rostedt@goodmis.org, mhiramat@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, varunrmallya@gmail.com Subject: [PATCH bpf v3 1/2] bpf: Reject sleepable kprobe_multi programs at attach time Date: Thu, 2 Apr 2026 00:41:25 +0530 Message-ID: <20260401191126.440683-1-varunrmallya@gmail.com> X-Mailer: git-send-email 2.53.0 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit kprobe.multi programs run in atomic/RCU context and cannot sleep. However, bpf_kprobe_multi_link_attach() did not validate whether the program being attached had the sleepable flag set, allowing sleepable helpers such as bpf_copy_from_user() to be invoked from a non-sleepable context. This causes a "sleeping function called from invalid context" splat: BUG: sleeping function called from invalid context at ./include/linux/uaccess.h:169 in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 1787, name: sudo preempt_count: 1, expected: 0 RCU nest depth: 2, expected: 0 Fix this by rejecting sleepable programs early in bpf_kprobe_multi_link_attach(), before any further processing. Fixes: 0dcac2725406 ("bpf: Add multi kprobe link") Signed-off-by: Varun R Mallya --- kernel/trace/bpf_trace.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c index 0b040a417442..af7079aa0f36 100644 --- a/kernel/trace/bpf_trace.c +++ b/kernel/trace/bpf_trace.c @@ -2752,6 +2752,10 @@ int bpf_kprobe_multi_link_attach(const union bpf_attr *attr, struct bpf_prog *pr if (!is_kprobe_multi(prog)) return -EINVAL; + /* kprobe_multi is not allowed to be sleepable. */ + if (prog->sleepable) + return -EINVAL; + /* Writing to context is not allowed for kprobes. */ if (prog->aux->kprobe_write_ctx) return -EINVAL; -- 2.53.0