id: correct getgroups usage

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 15 insertions, 16 deletions

diff --git a/coreutils/id.c b/coreutils/id.c
index bb950f9ec..399d25e34 100644
--- a/coreutils/id.c
+++ b/coreutils/id.c
@@ -117,7 +117,7 @@ static int print_user(uid_t id, const char *prefix)
 
 /* On error set *n < 0 and return >= 0
  * If *n is too small, update it and return < 0
- *  (ok to trash groups[] in both cases)
+ * (ok to trash groups[] in both cases)
  * Otherwise fill in groups[] and return >= 0
  */
 static int get_groups(const char *username, gid_t rgid, gid_t *groups, int *n)
@@ -131,20 +131,19 @@ static int get_groups(const char *username, gid_t rgid, gid_t *groups, int *n)
                 m = getgrouplist(username, rgid, groups, n);
                 /* I guess *n < 0 might indicate error. Anyway,
                  * malloc'ing -1 bytes won't be good, so: */
-                //if (*n < 0)
-                //      return 0;
-                //return m;
-                //commented out here, happens below anyway
-        } else {
-                /* On error -1 is returned, which ends up in *n */
-                int nn = getgroups(*n, groups);
-                /* 0: nn <= *n, groups[] was big enough; -1 otherwise */
-                m = - (nn > *n);
-                *n = nn;
+                if (*n < 0)
+                        return 0;
+                return m;
         }
-        if (*n < 0)
-                return 0; /* error, don't return < 0! */
-        return m;
+
+        *n = getgroups(*n, groups);
+        if (*n >= 0)
+                return *n;
+        /* Error */
+        if (errno == EINVAL) /* *n is too small? */
+                *n = getgroups(0, groups); /* get needed *n */
+        /* if *n >= 0, return -1 (got new *n), else return 0 (error): */
+        return -(*n >= 0);
 }
 
 int id_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
@@ -214,11 +213,11 @@ int id_main(int argc UNUSED_PARAM, char **argv)
                 /* We are supplying largish buffer, trying
                  * to not run get_groups() twice. That might be slow
                  * ("user database in remote SQL server" case) */
-                groups = xmalloc(64 * sizeof(gid_t));
+                groups = xmalloc(64 * sizeof(groups[0]));
                 n = 64;
                 if (get_groups(username, rgid, groups, &n) < 0) {
                         /* Need bigger buffer after all */
-                        groups = xrealloc(groups, n * sizeof(gid_t));
+                        groups = xrealloc(groups, n * sizeof(groups[0]));
                         get_groups(username, rgid, groups, &n);
                 }
                 if (n > 0) {