id: correct getgroups usage

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

diff --git a/coreutils/id.c b/coreutils/id.c
index bb950f9ec37f4431a1dab9785e1c628eb814c039..399d25e34232eda0f3c90d775543d66e4c9310d1 100644 (file)
--- 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) {