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alloca in compat-initgroups
- From: Thorsten Kukuk <kukuk at suse dot de>
- To: libc-alpha at sources dot redhat dot com
- Date: Mon, 19 Jul 2004 21:29:54 +0200
- Subject: alloca in compat-initgroups
- Organization: SuSE Linux AG, Nuernberg, Germany
Hi,
getgrent_next_nss() from compat-initgroups allocates a temporary
buffer with alloca. The size is NGROUPS_MAX * sizeof (gid_t).
While this was no problem with NGROUPS_MAX = 32, it is a problem
with multithreaded applications and kernel >= 2.6.5 (NGROUPS_MAX=65536).
I would suggest to use malloc instead:
2004-07-19 Thorsten Kukuk <kukuk@suse.de>
* nis/nss_compat/compat-initgroups.c(getgrent_next_nss): Don't
allocate memory for large temporary variables with alloca.
--- nis/nss_compat/compat-initgroups.c 28 Jun 2003 07:49:23 -0000 1.13
+++ nis/nss_compat/compat-initgroups.c 19 Jul 2004 11:13:17 -0000
@@ -1,4 +1,4 @@
-/* Copyright (C) 1998,1999,2000,2001,2002,2003 Free Software Foundation, Inc.
+/* Copyright (C) 1998,1999,2000,2001,2002,2003, 2004 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Thorsten Kukuk <kukuk@suse.de>, 1998.
@@ -242,7 +241,10 @@
if (nss_initgroups_dyn && nss_getgrgid_r)
{
long int mystart = 0, mysize = limit;
- gid_t *mygroupsp = __alloca (limit * sizeof (gid_t));
+ gid_t *mygroupsp = malloc (limit * sizeof (gid_t));
+
+ if (mygroupsp == NULL)
+ return NSS_STATUS_UNAVAIL;
/* For every gid in the list we get from the NSS module,
get the whole group entry. We need to do this, since we
@@ -280,8 +282,11 @@
check_and_add_group (user, group, start, size, groupsp,
limit, &grpbuf);
}
+
+ free (mygroupsp);
return NSS_STATUS_NOTFOUND;
}
+ free (mygroupsp);
}
/* If we come here, the NSS module does not support initgroups_dyn
--
Thorsten Kukuk http://www.suse.de/~kukuk/ kukuk@suse.de
SuSE Linux AG Maxfeldstr. 5 D-90409 Nuernberg
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