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Wed, 01 Apr 2026 06:49:37 -0700 (PDT) From: Varun R Mallya To: varunrmallya@gmail.com Cc: andrii@kernel.org, ast@kernel.org, bpf@vger.kernel.org, daniel@iogearbox.net, eddyz87@gmail.com, jolsa@kernel.org, kpsingh@kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, martin.lau@linux.dev, mathieu.desnoyers@efficios.com, mattbobrowski@google.com, memxor@gmail.com, mhiramat@kernel.org, rostedt@goodmis.org, song@kernel.org, yonghong.song@linux.dev Subject: [PATCH bpf] bpf: Reject sleepable kprobe_multi programs at attach time Date: Wed, 1 Apr 2026 19:19:21 +0530 Message-ID: <20260401134921.362148-1-varunrmallya@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: bpf@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: 0dcac272540613d41c05e89679e4ddb978b612f1 ("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