1174465 - CpuSampler::GetSystemLoad uses incorrect sscanf arguments

Status: RESOLVED FIXED

(Core :: WebRTC, defect)

Description

[q1]

CpuSampler::GetSystemLoad (38.0.1\media\webrtc\trunk\webrtc\base\cpumonitor.cc line 165) uses incorrect sscanf arguments at line 262:

258:  unsigned long long user;
259:  unsigned long long nice;
260:  unsigned long long system;
261:  unsigned long long idle;
262:  if (sscanf(statbuf.c_str(), "cpu %Lu %Lu %Lu %Lu",
263:             &user, &nice,
264:             &system, &idle) != 4) {
265:    LOG_ERR(LS_ERROR) << "Could not parse cpu info";
266:    return 0.f;
267:  }

"%Lu" is an invalid format specifier. Experiment shows that VC 2010 ignores the "L", and sets only the lower halves of the output arguments.

Probably the appropriate specifier is "%I64u" or "%lld", though there might still be a signed/unsigned issue there.

This bug does not appear to have any security consequences. I have marked it as a security bug only because I have already publicly reported one nonsecurity sscanf issue (https://bugzilla.mozilla.org/show_bug.cgi?id=1174455 ) and expect to find more, and I don't want to suggest to the wide world that it would be profitable to scan the code for them.

Comment 1

[Randell Jesup [:jesup] (needinfo me)]

We don't compile or use cpumonitor.cc - it's in an upstream imported package, and is part of "rtc_base" in gyp, not "rtc_base_approved" which is what we use from 'base'.

Comment 2

[q1]

I suggest adding a #error directive to this code so that no one accidentally introduces a bug later.

Comment 3

[q1]

That's odd: why did the status change from "invalid" to "fixed"?