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Date: Sat, 9 Jul 2005 15:13:40 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Alistair John Strachan <s0348365@sms.ed.ac.uk>
Cc: linux-kernel@vger.kernel.org, Arjan van de Ven <arjanv@infradead.org>,
       "David S. Miller" <davem@redhat.com>
Subject: Re: Realtime Preemption, 2.6.12, Beginners Guide?
Message-ID: <20050709131340.GA5925@elte.hu>
References: <200507061257.36738.s0348365@sms.ed.ac.uk> <200507081938.27815.s0348365@sms.ed.ac.uk> <20050708194827.GA22536@elte.hu> <200507082145.08877.s0348365@sms.ed.ac.uk> <20050709124105.GB4665@elte.hu>
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> (gdb) ####################################
> (gdb) # c02decd6, stack size:  460 bytes #
> (gdb) ####################################
> (gdb) 0xc02decd6 is in ip_getsockopt (net/ipv4/ip_sockglue.c:877).

----
this patch reduces the stack footprint of ip_getsockopt() from 460 bytes 
to 188 bytes. (note: needs review & testing because i did not excercise 
this multicast codepath.)

Signed-off-by: Ingo Molnar <mingo@elte.hu>

Index: linux/net/ipv4/ip_sockglue.c
===================================================================
--- linux.orig/net/ipv4/ip_sockglue.c
+++ linux/net/ipv4/ip_sockglue.c
@@ -1006,20 +1024,28 @@ int ip_getsockopt(struct sock *sk, int l
 		}
 		case MCAST_MSFILTER:
 		{
-			struct group_filter gsf;
+			struct group_filter *gsf;
 			int err;
 
+			gsf = kmalloc(sizeof(*gsf), GFP_KERNEL);
+			if (!gsf) {
+				release_sock(sk);
+				return -ENOMEM;
+			}
 			if (len < GROUP_FILTER_SIZE(0)) {
 				release_sock(sk);
+				kfree(gsf);
 				return -EINVAL;
 			}
-			if (copy_from_user(&gsf, optval, GROUP_FILTER_SIZE(0))) {
+			if (copy_from_user(gsf, optval, GROUP_FILTER_SIZE(0))) {
 				release_sock(sk);
+				kfree(gsf);
 				return -EFAULT;
 			}
-			err = ip_mc_gsfget(sk, &gsf,
+			err = ip_mc_gsfget(sk, gsf,
 				(struct group_filter __user *)optval, optlen);
 			release_sock(sk);
+			kfree(gsf);
 			return err;
 		}
 		case IP_PKTOPTIONS: