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From: Nobuhiro Iwamatsu <>
Cc:, David Ahern <>,
	Andrey Konovalov <>,
	"David S . Miller" <>,
	Nobuhiro Iwamatsu <>
Subject: [PATCH] net: handle no dst on skb in icmp6_send
Date: Wed, 13 May 2020 18:04:51 +0900	[thread overview]
Message-ID: <> (raw)

From: David Ahern <>

commit 79dc7e3f1cd323be4c81aa1a94faa1b3ed987fb2 upstream.

Andrey reported the following while fuzzing the kernel with syzkaller:

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] SMP KASAN
Modules linked in:
CPU: 0 PID: 3859 Comm: a.out Not tainted 4.9.0-rc6+ #429
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
task: ffff8800666d4200 task.stack: ffff880067348000
RIP: 0010:[<ffffffff833617ec>]  [<ffffffff833617ec>]
icmp6_send+0x5fc/0x1e30 net/ipv6/icmp.c:451
RSP: 0018:ffff88006734f2c0  EFLAGS: 00010206
RAX: ffff8800666d4200 RBX: 0000000000000000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: dffffc0000000000 RDI: 0000000000000018
RBP: ffff88006734f630 R08: ffff880064138418 R09: 0000000000000003
R10: dffffc0000000000 R11: 0000000000000005 R12: 0000000000000000
R13: ffffffff84e7e200 R14: ffff880064138484 R15: ffff8800641383c0
FS:  00007fb3887a07c0(0000) GS:ffff88006cc00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000000 CR3: 000000006b040000 CR4: 00000000000006f0
 ffff8800666d4200 ffff8800666d49f8 ffff8800666d4200 ffffffff84c02460
 ffff8800666d4a1a 1ffff1000ccdaa2f ffff88006734f498 0000000000000046
 ffff88006734f440 ffffffff832f4269 ffff880064ba7456 0000000000000000
Call Trace:
 [<ffffffff83364ddc>] icmpv6_param_prob+0x2c/0x40 net/ipv6/icmp.c:557
 [<     inline     >] ip6_tlvopt_unknown net/ipv6/exthdrs.c:88
 [<ffffffff83394405>] ip6_parse_tlv+0x555/0x670 net/ipv6/exthdrs.c:157
 [<ffffffff8339a759>] ipv6_parse_hopopts+0x199/0x460 net/ipv6/exthdrs.c:663
 [<ffffffff832ee773>] ipv6_rcv+0xfa3/0x1dc0 net/ipv6/ip6_input.c:191

icmp6_send / icmpv6_send is invoked for both rx and tx paths. In both
cases the dst->dev should be preferred for determining the L3 domain
if the dst has been set on the skb. Fallback to the skb->dev if it has
not. This covers the case reported here where icmp6_send is invoked on
Rx before the route lookup.

Fixes: 5d41ce29e ("net: icmp6_send should use dst dev to determine L3 domain")
Reported-by: Andrey Konovalov <>
Signed-off-by: David Ahern <>
Signed-off-by: David S. Miller <>
Signed-off-by: Nobuhiro Iwamatsu (CIP) <>
 net/ipv6/icmp.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/icmp.c b/net/ipv6/icmp.c
index d21e81cd6120e..fa96e05cf22be 100644
--- a/net/ipv6/icmp.c
+++ b/net/ipv6/icmp.c
@@ -445,8 +445,10 @@ static void icmp6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
 	if (__ipv6_addr_needs_scope_id(addr_type))
 		iif = skb->dev->ifindex;
-	else
-		iif = l3mdev_master_ifindex(skb_dst(skb)->dev);
+	else {
+		dst = skb_dst(skb);
+		iif = l3mdev_master_ifindex(dst ? dst->dev : skb->dev);
+	}
 	 *	Must not send error if the source does not uniquely

             reply	other threads:[~2020-05-13  9:05 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-13  9:04 Nobuhiro Iwamatsu [this message]
2020-05-13  9:15 ` [PATCH] net: handle no dst on skb in icmp6_send nobuhiro1.iwamatsu
2020-05-13  9:23   ` Greg KH
  -- strict thread matches above, loose matches on Subject: below --
2016-11-28  2:52 David Ahern
2016-11-28 21:13 ` David Miller
2016-12-08 14:04   ` Hannes Frederic Sowa
2016-12-28  2:36     ` David Miller

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