From fd9858317a3d06c94ad8c1c420e6b5c376f5a92e Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Thu, 21 Mar 2019 17:08:30 +0000 Subject: [PATCH] trace: handle tracefs path truncation If the tracefs mountpoint has a very long path we may exceed PATH_MAX. This is a system misconfiguration and the user must resolve it so that applications can perform path-based system calls successfully. This issue does not occur on real-world systems since tracefs is mounted on /sys/kernel/debug/tracing/, but the compiler is smart enough to foresee the possibility and warn about the unchecked snprintf(3) return value. This patch fixes the compiler warning. Reported-by: Markus Armbruster Signed-off-by: Stefan Hajnoczi Reviewed-by: Markus Armbruster Reviewed-by: Liam Merwick Message-id: 20190321170831.6539-2-stefanha@redhat.com Message-Id: <20190321170831.6539-2-stefanha@redhat.com> Signed-off-by: Stefan Hajnoczi --- trace/ftrace.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/trace/ftrace.c b/trace/ftrace.c index 61692a8682..9749543d9b 100644 --- a/trace/ftrace.c +++ b/trace/ftrace.c @@ -53,7 +53,11 @@ bool ftrace_init(void) } if (tracefs_found) { - snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir); + if (snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir) + >= sizeof(path)) { + fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n"); + return false; + } trace_fd = open(path, O_WRONLY); if (trace_fd < 0) { if (errno == EACCES) { @@ -72,7 +76,11 @@ bool ftrace_init(void) } close(trace_fd); } - snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir); + if (snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir) + >= sizeof(path)) { + fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n"); + return false; + } trace_marker_fd = open(path, O_WRONLY); if (trace_marker_fd < 0) { perror("Could not open ftrace 'trace_marker' file");