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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 <armbru@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Liam Merwick <liam.merwick@oracle.com> Message-id: 20190321170831.6539-2-stefanha@redhat.com Message-Id: <20190321170831.6539-2-stefanha@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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@ -53,7 +53,11 @@ bool ftrace_init(void)
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}
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if (tracefs_found) {
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snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir);
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if (snprintf(path, PATH_MAX, "%s%s/tracing_on", mount_point, subdir)
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>= sizeof(path)) {
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fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n");
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return false;
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}
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trace_fd = open(path, O_WRONLY);
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if (trace_fd < 0) {
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if (errno == EACCES) {
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@ -72,7 +76,11 @@ bool ftrace_init(void)
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}
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close(trace_fd);
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}
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snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir);
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if (snprintf(path, PATH_MAX, "%s%s/trace_marker", mount_point, subdir)
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>= sizeof(path)) {
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fprintf(stderr, "Using tracefs mountpoint would exceed PATH_MAX\n");
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return false;
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}
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trace_marker_fd = open(path, O_WRONLY);
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if (trace_marker_fd < 0) {
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perror("Could not open ftrace 'trace_marker' file");
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