I'm not sure the best way to fix this, but I have located the problem.
I've found this bug to be caused by a Debian patch
"ps_supgid_display.patch" which was initially from the bug report at
http://bugs.debian.org/506303
When any /proc/<pid>/status has more than 1024 characters before the end
of the Groups line, an infinite loop is entered because the loop never
finds the "\n" character it expected. Looking back at the strace, the
read of "/proc/11860/status" is truncated. A succesful part of the
strace is
stat("/proc/1110", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0
open("/proc/1110/stat", O_RDONLY) = 6
read(6, "1110 (npcd) S 1 1108 1108 0 -1 4202816 509903 56395239 0 129102 205
836 161563 37679 20 0 1 0 3191 243957760 263 18446744073709551615 4194304
4219268 140737259370048 140737259368256 140200938633277 0 0 0 16387
18446744071579436968 0 0 17 0 0 0 1348 0 0\n", 1023) = 253
While the loop runs, it keeps allocating more memory for the array of Group IDs
that it has found associated with the process until it fails because there
isn't enough memory to allocate.
The while loop below from the patch is what runs infinitely. The xrealloc
allocates more memory, doubling the amount it wants each time the loop thinks
the array is filled.
+ case_Groups:
+ isupgid = 0;
+ if (*S != '\n'){ // Is there any supplementary group ?
+ P->supgid = (int *) xmalloc(0x0004 * sizeof(int));
+ int vctsize = 0x0004;
+ while (S[1] != '\n' && isupgid<INT_MAX){ // There is one blank
before '\n'
+ if (isupgid == vctsize){
+ vctsize *= 2;
+ P->supgid = (int *)xrealloc(P->supgid,vctsize * sizeof(int));
+ }
+ P->supgid[isupgid++] = strtol(S,&S,10);
+ P->nsupgid++;
+ }
+ }
+ continue;
** Bug watch added: Debian Bug tracker #506303
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=506303
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https://bugs.launchpad.net/bugs/1150413
Title:
Cannot allocate memory if process owned by user with large number of
groups
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