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library: address major bug in the 'listed_nextpid' guy

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Ever since 2003, the 'listed_nextpid' routine has been
misrepresenting its duties. Far from finding processes
in a list given to openproc, it just inserted the next
pid in that list into the passed proc_t as BOTH a tgid
and tid. There was no attempt to validate such values.

The net result is that tid & tgid were valid only with
a thread group leader. When called with a pid for some
sibling thread, the resulting tgid would be incorrect.

With this commit, our little function will now attempt
to validate both the tid and tgid. If this should fail
then the fallback position will be the same as what we
inherited. So we're no worse off & likely much better.

[ note that calling the function with a thread's pid ]
[ likely stems from 2011 when a 'readeither' routine ]
[ was added which dealt with both tasks and threads! ]

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner 2021-08-10 00:00:00 -05:00 committed by Craig Small
parent f1aad95cd1
commit 96e2220068
1 changed files with 22 additions and 9 deletions
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31
proc/readproc.c
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@ -1405,16 +1405,29 @@ static int simple_nexttid(PROCTAB *restrict const PT, const proc_t *restrict con
////////////////////////////////////////////////////////////////////////////////// //////////////////////////////////////////////////////////////////////////////////
// This "finds" processes in a list that was given to openproc(). // This "finds" processes in a list that was given to openproc().
// Return non-zero on success. (tgid was handy) // Return non-zero on success. (tgid is a real headache)
static int listed_nextpid(PROCTAB *restrict const PT, proc_t *restrict const p) { static int listed_nextpid (PROCTAB *PT, proc_t *p) {
char *restrict const path = PT->path; static struct utlbuf_s ub = { NULL, 0 };
pid_t tgid = *(PT->pids)++; pid_t pid = *(PT->pids)++;
if(tgid){ char *path = PT->path;
snprintf(path, PROCPATHLEN, "/proc/%d", tgid);
p->tgid = tgid; if (pid) {
p->tid = tgid; // they match for leaders snprintf(path, PROCPATHLEN, "/proc/%d", pid);
p->tid = p->tgid = pid; // this tgid may be a huge fib |
/* the 'status' directory is the only place where we find the |
task's real tgid. it's a bit expensive, but remember we're |
dealing with fewer processes, unlike the other 'next' guys |
(plus we need not parse the whole thing like status2proc)! | */
if (file2str(path, "status", &ub) != -1) {
char *str = strstr(ub.buf, "Tgid:");
if (str) {
p->tgid = atoi(str + 5); // this tgid is the proper one |
}
}
} }
return tgid; return pid;
} }