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Mon, 08 Jun 2026 17:44:51 -0700 (PDT) From: Samuel Moelius To: Steven Rostedt Cc: Samuel Moelius , Masami Hiramatsu , Mark Rutland , linux-kernel@vger.kernel.org (open list:FUNCTION HOOKS (FTRACE)), linux-trace-kernel@vger.kernel.org (open list:FUNCTION HOOKS (FTRACE)) Subject: [PATCH] samples/ftrace: reject zero ftrace-ops call count Date: Tue, 9 Jun 2026 00:44:23 +0000 Message-ID: <20260609004422.1239735.f6c06011af32.ftrace-ops-zero-function-calls-div0@trailofbits.com> X-Mailer: git-send-email 2.43.0 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 The ftrace-ops sample exposes nr_function_calls as a module parameter and uses it as the divisor when printing the measured time per call. Loading the module with nr_function_calls=0 skips the benchmark loop and then divides the elapsed time by zero, crashing the kernel during sample module initialization. Reject a zero call count before registering any ftrace ops. Assisted-by: Codex:gpt-5.5-cyber-preview Signed-off-by: Samuel Moelius --- samples/ftrace/ftrace-ops.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/samples/ftrace/ftrace-ops.c b/samples/ftrace/ftrace-ops.c index 68d6685c80bd..d5adaa61484f 100644 --- a/samples/ftrace/ftrace-ops.c +++ b/samples/ftrace/ftrace-ops.c @@ -190,6 +190,11 @@ static int __init ftrace_ops_sample_init(void) tracer_irrelevant = ops_func_count; } + if (!nr_function_calls) { + pr_err("nr_function_calls must be non-zero\n"); + return -EINVAL; + } + pr_info("registering:\n" " relevant ops: %u\n" " tracee: %ps\n" -- 2.43.0