Hello!
In coreutils/id.c get_groups() gets groups list for further printing out
on screen. According to id's main function - return value from
get_groups is expected even < 0 in order to extend (xrealloc) the
list size for the groups in case if there's more than 64:
> 123 int id_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
> 124 int id_main(int argc UNUSED_PARAM, char **argv)
> 125 {
...
> 180 n = 64;
> 181 if (get_groups(username, rgid, groups, &n) < 0) {
> 182 /* Need bigger buffer after all */
> 183 groups = xrealloc(groups, n * sizeof(gid_t));
> 184 get_groups(username, rgid, groups, &n);
> 185 }
> 186 if (n > 0) {
But get_groups() allowed to return only >=0 value:
> 96 static int get_groups(const char *username, gid_t rgid, gid_t *groups,
> int *n)
...
> 118 if (*n < 0)
> 119 return 0; /* error, don't return < 0! */
> 120 return m;
> 121 }
And as a result - no way to get more than 64 groups, it goes strait to the
bb_err_msg:
> 196 } else if (n < 0) { /* error in get_groups() */
> 197 if (ENABLE_DESKTOP)
> 198 bb_error_msg_and_die("can't get
> groups");
> 199 return EXIT_FAILURE;
> 200 }
Is there any reason for such kind of restriction in get_groups? I'm suggesting
to substitute this restriction with the call to "getgroups(0, groups)", to get
an
actual amount of groups before returning -1. In this case we're calling
getgroups()
3 times. But only if we have more than 64 groups, it's a rare case. Another way
-
is to call getgroups() twice but always, first time to get amount of groups and
then the actual groups list. I guess to call three times but in rare cases is
better than twice but always.
Patch is in attachment:
>From 3a99379834788c6169a7dd992473524c9652e6a4 Mon Sep 17 00:00:00 2001
Alexey Fomenko (1):
id: fix return value when trying to get more than 64 groups
coreutils/id.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
--
1.7.3.4
Br,
Alex F
>From 3a99379834788c6169a7dd992473524c9652e6a4 Mon Sep 17 00:00:00 2001
From: Alexey Fomenko <[email protected]>
Date: Mon, 13 Jun 2011 14:55:10 +0300
Subject: [PATCH] id: fix return value when trying to get more than 64 groups
Signed-off-by: Alexey Fomenko <[email protected]>
---
coreutils/id.c | 5 +++--
1 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/coreutils/id.c b/coreutils/id.c
index aa6ae47..dd29fe6 100644
--- a/coreutils/id.c
+++ b/coreutils/id.c
@@ -115,8 +115,9 @@ static int get_groups(const char *username, gid_t rgid, gid_t *groups, int *n)
m = - (nn > *n);
*n = nn;
}
- if (*n < 0)
- return 0; /* error, don't return < 0! */
+ if (*n < 0) {
+ *n = getgroups(0, groups); /* error, get the actual amount ot groups */
+ }
return m;
}
--
1.7.3.4
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