net: ipmr/ip6mr: fix potential out-of-bounds vif_table access

commit 65782983286f43e2b14eec2d7287171a9957a754

Author: Patrick McHardy <[email protected]>
Date:   Wed Mar 17 16:54:20 2010 +0100

net: ipmr/ip6mr: fix potential out-of-bounds vif_table access

mfc_parent of cache entries is used to index into the vif_table and is initialised from mfcctl->mfcc_parent. This can take values of to 2^16-1, while the vif_table has only MAXVIFS (32) entries. The same problem affects ip6mr.

Refuse invalid values to fix a potential out-of-bounds access. Unlike the other validity checks, this is checked in ipmr_mfc_add() instead of the setsockopt handler since its unused in the delete path and might be uninitialized.

index 8582e12..0b9d03c 100644
@@ -802,6 +802,9 @@ static int ipmr_mfc_add(struct net *net, struct mfcctl *mfc, int mrtsock)
 	int line;
 	struct mfc_cache *uc, *c, **cp;
 
+	if (mfc->mfcc_parent >= MAXVIFS)
+		return -ENFILE;
+
 	line = MFC_HASH(mfc->mfcc_mcastgrp.s_addr, mfc->mfcc_origin.s_addr);
 
 	for (cp = &net->ipv4.mfc_cache_array[line];

index 52e0f74..23e4ac0 100644
@@ -1113,6 +1113,9 @@ static int ip6mr_mfc_add(struct net *net, struct mf6cctl *mfc, int mrtsock)
 	unsigned char ttls[MAXMIFS];
 	int i;
 
+	if (mfc->mf6cc_parent >= MAXMIFS)
+		return -ENFILE;
+
 	memset(ttls, 255, MAXMIFS);
 	for (i = 0; i < MAXMIFS; i++) {
 		if (IF_ISSET(i, &mfc->mf6cc_ifset))

My appologies for using git-show again. Correctly formatted patch attached.

mfc_parent of cache entries is used to index into the vif_table and is initialised from mfcctl->mfcc_parent. This can take values of to 2^16-1, while the vif_table has only MAXVIFS (32) entries. The same problem affects ip6mr.

Refuse invalid values to fix a potential out-of-bounds access. Unlike the other validity checks, this is checked in ipmr_mfc_add() instead of the setsockopt handler since its unused in the delete path and might be uninitialized.

---
 net/ipv4/ipmr.c  |    3 +++
 net/ipv6/ip6mr.c |    3 +++
 2 files changed, 6 insertions(+), 0 deletions(-)

index 8582e12..0b9d03c 100644
@@ -802,6 +802,9 @@ static int ipmr_mfc_add(struct net *net, struct mfcctl *mfc, int mrtsock)
 	int line;
 	struct mfc_cache *uc, *c, **cp;
 
+	if (mfc->mfcc_parent >= MAXVIFS)
+		return -ENFILE;
+
 	line = MFC_HASH(mfc->mfcc_mcastgrp.s_addr, mfc->mfcc_origin.s_addr);
 
 	for (cp = &net->ipv4.mfc_cache_array[line];

index 52e0f74..23e4ac0 100644
@@ -1113,6 +1113,9 @@ static int ip6mr_mfc_add(struct net *net, struct mf6cctl *mfc, int mrtsock)
 	unsigned char ttls[MAXMIFS];
 	int i;
 
+	if (mfc->mf6cc_parent >= MAXMIFS)
+		return -ENFILE;
+
 	memset(ttls, 255, MAXMIFS);
 	for (i = 0; i < MAXMIFS; i++) {
 		if (IF_ISSET(i, &mfc->mf6cc_ifset))

1.6.5.7

From: Patrick McHardy <[email protected]>
Date: Wed, 17 Mar 2010 17:04:14 +0100

Applied, thanks.