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Harden the extraction of boot time for the Linux platform 

There is a possible path - albeit theoretical really - through
the btime initialization code in Linux ProcessList_new(), when
String_startsWith() is always false, which can result in btime
not being initialized.

This commit refactors the code to remove that possibility.
This commit is contained in:
Nathan Scott 2020-12-14 12:16:32 +11:00
parent a3db2da4a7
commit b7836515e8
1 changed files with 11 additions and 12 deletions
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23
linux/LinuxProcessList.c
View File

@ -226,26 +226,25 @@ ProcessList* ProcessList_new(UsersTable* usersTable, Hashtable* pidMatchList, ui
// Test /proc/PID/smaps_rollup availability (faster to parse, Linux 4.14+)
this->haveSmapsRollup = (access(PROCDIR "/self/smaps_rollup", R_OK) == 0);
// Read btime
// Read btime (the kernel boot time, as number of seconds since the epoch)
{
FILE* statfile = fopen(PROCSTATFILE, "r");
if (statfile == NULL) {
if (statfile == NULL)
CRT_fatalError("Cannot open " PROCSTATFILE);
}
while (true) {
char buffer[PROC_LINE_LENGTH + 1];
if (fgets(buffer, sizeof(buffer), statfile) == NULL) {
CRT_fatalError("No btime in " PROCSTATFILE);
} else if (String_startsWith(buffer, "btime ")) {
if (sscanf(buffer, "btime %lld\n", &btime) != 1) {
CRT_fatalError("Failed to parse btime from " PROCSTATFILE);
}
if (fgets(buffer, sizeof(buffer), statfile) == NULL)
break;
}
if (String_startsWith(buffer, "btime ") == false)
continue;
if (sscanf(buffer, "btime %lld\n", &btime) == 1)
break;
CRT_fatalError("Failed to parse btime from " PROCSTATFILE);
}
fclose(statfile);
if (!btime)
CRT_fatalError("No btime in " PROCSTATFILE);
}
// Initialize CPU count