linux-kernel - [PATCH] trace-cmd:show: be picky on user argument 'cpu'

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Date:   Wed,  6 Dec 2017 06:12:12 +0100
From:   Federico Vaga <federico.vaga@...a.pv.it>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Federico Vaga <federico.vaga@...a.pv.it>
Subject: [PATCH] trace-cmd:show: be picky on user argument 'cpu'

Before this patch the following command worked without errors:

    trace-cmd show -c b

This command opens the CPU0 files. From `strace(1)`:

    openat(AT_FDCWD, "/sys/kernel/tracing/per_cpu/cpu0/trace", O_RDONLY) = 3

Signed-off-by: Federico Vaga <federico.vaga@...a.pv.it>
---
 trace-show.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/trace-show.c b/trace-show.c
index f13db31..7d04012 100644
--- a/trace-show.c
+++ b/trace-show.c
@@ -149,7 +149,14 @@ void trace_show(int argc, char **argv)
 		file = "snapshot";
 
 	if (cpu) {
-		snprintf(cpu_path, 128, "per_cpu/cpu%d/%s", atoi(cpu), file);
+		char *endptr;
+		long val;
+
+		errno = 0;
+		val = strtol(cpu, &endptr, 0);
+		if (errno || cpu == endptr)
+			die("Invalid CPU index '%s'", cpu);
+		snprintf(cpu_path, 128, "per_cpu/cpu%ld/%s", val, file);
 		file = cpu_path;
 	}
 
-- 
2.14.3