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library: avoid problems involving 'supgid' mishandling

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Following that patch referenced below, the top SUPGRPS
field would produce a segmentation fault and ps SUPGRP
would often show "(null)". Such problems resulted from
some faulty logic in the status2proc() routine dealing
with 'Groups' (supgid) which served as a source field.

For many processes the original code produced an empty
string which prevented conversion to the expected "-".
Moreover, prior to release 3.3.15 such an empty string
will become 0 after strtol() which pwcache_get_group()
translates to 'root' yielding very misleading results.

So, now we'll check for empty '/proc/#/status/Groups:'
fields & consistently provide a "-" value for callers.

[ we'll also protect against future problems in that ]
[ new qualys logic by always ensuring valid 'supgrp' ]
[ pointers - logic which revealed our original flaw! ]

Reference(s):
. original qualys patch
0071-proc-readproc.c-Harden-supgrps_from_supgids.patch

Signed-off-by: Jim Warner <james.warner@comcast.net>
This commit is contained in:
Jim Warner 2018-06-03 00:00:00 -05:00 committed by Craig Small
parent 80e210d38e
commit 50ae55ef10
1 changed files with 13 additions and 8 deletions
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21
proc/readproc.c
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@ -393,17 +393,20 @@ ENTER(0x220);
P->vm_swap = (unsigned long)strtol(S,&S,10);
continue;
case_Groups:
{ char *nl = strchr(S, '\n');
size_t j = nl ? (size_t)(nl - S) : strlen(S);
{ char *ss = S, *nl = strchr(S, '\n');
size_t j;
#ifdef FALSE_THREADS
if (IS_THREAD(P)) continue;
#endif
while (' ' == *ss || '\t' == *ss) ss++;
if (ss >= nl) continue;
j = nl ? (size_t)(nl - ss) : strlen(ss);
if (j > 0 && j < INT_MAX) {
P->supgid = malloc(j+1); // +1 in case space disappears
if (!P->supgid)
return 1;
memcpy(P->supgid, S, j);
memcpy(P->supgid, ss, j);
if (' ' != P->supgid[--j]) ++j;
P->supgid[j] = '\0'; // whack the space or the newline
for ( ; j; j--)
@ -482,11 +485,9 @@ static int supgrps_from_supgids (proc_t *p) {
#ifdef FALSE_THREADS
if (IS_THREAD(p)) return 0;
#endif
if (!p->supgid || '-' == *p->supgid) {
if (!(p->supgrp = strdup("-")))
return 1;
return 0;
}
if (!p->supgid || '-' == *p->supgid)
goto wrap_up;
s = p->supgid;
t = 0;
do {
@ -511,6 +512,10 @@ static int supgrps_from_supgids (proc_t *p) {
t += len;
} while (*s);
wrap_up:
if (!p->supgrp
&& !(p->supgrp = strdup("-")))
return 1;
return 0;
}