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igmp_sendpkt() expects ip_output() to set 'imo.imo_multicast_ttl' into 

'ip->ip_ttl'; but ip_output() won't if the target is not a multicast
address, meaning that the uninitialized 'ip->ip_ttl' byte gets sent to
the network. This leaks one byte of kernel heap.

Fix this by filling 'ip->ip_ttl' with a TTL of one.

Found by KMSAN.

Reported-by: syzbot+e49f7b8a8fec5a477c9a@syzkaller.appspotmail.com
This commit is contained in:
maxv 2020-05-15 06:34:34 +00:00
parent 5b7653f57e
commit 145523e834
1 changed files with 3 additions and 2 deletions
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5
sys/netinet/igmp.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: igmp.c,v 1.69 2018/09/14 05:09:51 maxv Exp $ */
/* $NetBSD: igmp.c,v 1.70 2020/05/15 06:34:34 maxv Exp $ */
/*
* Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
@ -40,7 +40,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: igmp.c,v 1.69 2018/09/14 05:09:51 maxv Exp $");
__KERNEL_RCSID(0, "$NetBSD: igmp.c,v 1.70 2020/05/15 06:34:34 maxv Exp $");
#ifdef _KERNEL_OPT
#include "opt_mrouting.h"
@ -613,6 +613,7 @@ igmp_sendpkt(struct in_multi *inm, int type)
ip->ip_tos = 0;
ip->ip_len = htons(sizeof(struct ip) + IGMP_MINLEN);
ip->ip_off = htons(0);
ip->ip_ttl = IP_DEFAULT_MULTICAST_TTL;
ip->ip_p = IPPROTO_IGMP;
ip->ip_src = zeroin_addr;
ip->ip_dst = inm->inm_addr;