ps: allow large list of groups

Current linux kernels output no more than 32 groups
in /proc/{pid}/status.

Plan is to increase this limit.

This patch allows ps to not core dump if the buffer used to read status
file was too small.

# ps aux
Signal 11 (SEGV) caught by ps (procps-ng version 3.3.3).
ps:display.c:59: please report this bug

Also increases the size of the buffer from 1024 to 4096, since even with
32 groups we are close to the limit.

cat /proc/12731/status | wc
     39     128     961

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/proc/readproc.c b/proc/readproc.c
index 63dbd5c..162cbad 100644
--- a/proc/readproc.c
+++ b/proc/readproc.c
@@ -353,7 +353,9 @@ ENTER(0x220);
         P->vm_swap = strtol(S,&S,10);
         continue;
     case_Groups:
-    {   int j = strchr(S, '\n') - S;        // currently lines end space + \n
+    {   char *nl = strchr(S, '\n');
+        int j = nl ? (nl - S) : strlen(S);
+
         if (j) {
             P->supgid = xmalloc(j+1);       // +1 in case space disappears
             memcpy(P->supgid, S, j);
@@ -735,7 +737,7 @@ int read_cmdline(char *restrict const dst, unsigned sz, unsigned pid) {
 // room to spare.
 static proc_t* simple_readproc(PROCTAB *restrict const PT, proc_t *restrict const p) {
     static struct stat sb;     // stat() buffer
-    static char sbuf[1024];    // buffer for stat,statm,status
+    static char sbuf[4096];    // buffer for stat,statm,status
     char *restrict const path = PT->path;
     unsigned flags = PT->flags;
 
@@ -841,7 +843,7 @@ next_proc:
 // path is a path to the task, with some room to spare.
 static proc_t* simple_readtask(PROCTAB *restrict const PT, const proc_t *restrict const p, proc_t *restrict const t, char *restrict const path) {
     static struct stat sb;     // stat() buffer
-    static char sbuf[1024];    // buffer for stat,statm,status
+    static char sbuf[4096];    // buffer for stat,statm,status
     unsigned flags = PT->flags;
 
     if (unlikely(stat(path, &sb) == -1))        /* no such dirent (anymore) */
@@ -1384,7 +1386,7 @@ proc_data_t *readproctab3 (int(*want_task)(proc_t *buf), PROCTAB *restrict const
  * and filled out proc_t structure.
  */
 proc_t * get_proc_stats(pid_t pid, proc_t *p) {
-	static char path[32], sbuf[1024];
+	static char path[32], sbuf[4096];
 	struct stat statbuf;
 
 	sprintf(path, "/proc/%d", pid);