From: David Laight <David.Laight@ACULAB.COM>
To: 'Tadeusz Struk' <tadeusz.struk@linaro.org>,
"davem@davemloft.net" <davem@davemloft.net>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
David Ahern <dsahern@kernel.org>,
Jakub Kicinski <kuba@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
Andrii Nakryiko <andrii@kernel.org>,
Martin KaFai Lau <kafai@fb.com>, Song Liu <songliubraving@fb.com>,
Yonghong Song <yhs@fb.com>,
John Fastabend <john.fastabend@gmail.com>,
KP Singh <kpsingh@kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"bpf@vger.kernel.org" <bpf@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"stable@vger.kernel.org" <stable@vger.kernel.org>,
"syzbot+e223cf47ec8ae183f2a0@syzkaller.appspotmail.com"
<syzbot+e223cf47ec8ae183f2a0@syzkaller.appspotmail.com>
Subject: RE: [PATCH] net: ipv6: fix invalid alloclen in __ip6_append_data
Date: Tue, 8 Mar 2022 02:58:18 +0000 [thread overview]
Message-ID: <14626165dad64bbaabed58ba7d59e523@AcuMS.aculab.com> (raw)
In-Reply-To: <20220308000146.534935-1-tadeusz.struk@linaro.org>
From: Tadeusz Struk
> Sent: 08 March 2022 00:02
>
> Syzbot found a kernel bug in the ipv6 stack:
> LINK: https://syzkaller.appspot.com/bug?id=205d6f11d72329ab8d62a610c44c5e7e25415580
>
> The reproducer triggers it by sending an invalid message via sendmmsg() call,
> which triggers skb_over_panic, and crashes the kernel:
>
> skbuff: skb_over_panic: text:ffffffff84647fb4 len:65575 put:65575
> head:ffff888109ff0000 data:ffff888109ff0088 tail:0x100af end:0xfec0
> dev:<NULL>
>
> ------------[ cut here ]------------
> kernel BUG at net/core/skbuff.c:113!
> PREEMPT SMP KASAN
> CPU: 1 PID: 1818 Comm: repro Not tainted 5.17.0-rc7-dirty #9
> Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1.fc35
> RIP: 0010:skb_panic+0x173/0x175
> RSP: 0018:ffffc900015bf3b8 EFLAGS: 00010282
> RAX: 0000000000000090 RBX: ffff88810e848c80 RCX: 0000000000000000
> RDX: ffff88810fd84300 RSI: ffffffff814fa5ef RDI: fffff520002b7e69
> RBP: ffffc900015bf420 R08: 0000000000000090 R09: 0000000000000000
> R10: ffffffff814f55f4 R11: 203a666675626b73 R12: ffffffff855bff80
> R13: ffffffff84647fb4 R14: 0000000000010027 R15: ffffffff855bf420
> FS: 0000000000c8b3c0(0000) GS:ffff88811b100000(0000) knlGS:0000000000000000
> CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
> CR2: 0000000020000040 CR3: 0000000106b68000 CR4: 0000000000150ea0
> Call Trace:
> <TASK>
> skb_put.cold+0x23/0x23
> __ip6_append_data.isra.0.cold+0x396/0xe3a
> ip6_append_data+0x1e5/0x320
> rawv6_sendmsg.cold+0x1618/0x2ba9
> inet_sendmsg+0x9e/0xe0
> sock_sendmsg+0xd7/0x130
> ____sys_sendmsg+0x381/0x8a0
> ___sys_sendmsg+0x100/0x170
> __sys_sendmmsg+0x26c/0x3b7
> __x64_sys_sendmmsg+0xb2/0xbd
> do_syscall_64+0x35/0xb0
> entry_SYSCALL_64_after_hwframe+0x44/0xae
>
> The reproducer can be found here:
> LINK: https://syzkaller.appspot.com/text?tag=ReproC&x=1648c83fb00000
> This can be fixed by increasing the alloclen in case it is smaller than
> fraglen in __ip6_append_data().
>
>
> Reported-by: syzbot+e223cf47ec8ae183f2a0@syzkaller.appspotmail.com
> Signed-off-by: Tadeusz Struk <tadeusz.struk@linaro.org>
> ---
> net/ipv6/ip6_output.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
> index 4788f6b37053..622345af323e 100644
> --- a/net/ipv6/ip6_output.c
> +++ b/net/ipv6/ip6_output.c
> @@ -1629,6 +1629,13 @@ static int __ip6_append_data(struct sock *sk,
> err = -EINVAL;
> goto error;
> }
> + if (unlikely(alloclen < fraglen)) {
> + if (printk_ratelimit())
> + pr_warn("%s: wrong alloclen: %d, fraglen: %d",
> + __func__, alloclen, fraglen);
> + alloclen = fraglen;
> + }
> +
Except that is a valid case, see a few lines higher:
alloclen = min_t(int, fraglen, MAX_HEADER);
pagedlen = fraglen - alloclen;
You need to report the input values that cause the problem later on.
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2022-03-08 2:58 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-08 0:01 [PATCH] net: ipv6: fix invalid alloclen in __ip6_append_data Tadeusz Struk
2022-03-08 2:58 ` David Laight [this message]
2022-03-08 15:43 ` Tadeusz Struk
2022-03-08 18:18 ` David Ahern
2022-03-08 19:46 ` Tadeusz Struk
2022-03-09 5:01 ` David Ahern
2022-03-09 21:37 ` Tadeusz Struk
2022-03-10 14:39 ` Willem de Bruijn
2022-03-10 16:06 ` Tadeusz Struk
2022-03-10 17:32 ` Willem de Bruijn
2022-03-10 21:14 ` Tadeusz Struk
2022-03-10 22:13 ` [PATCH v2] net: ipv6: fix skb_over_panic " Tadeusz Struk
2022-03-10 22:18 ` David Laight
2022-03-10 22:30 ` Jakub Kicinski
2022-03-10 22:42 ` Tadeusz Struk
2022-03-10 22:43 ` Willem de Bruijn
2022-03-10 23:04 ` Tadeusz Struk
2022-03-10 23:05 ` David Laight
2022-03-10 23:25 ` [PATCH v3] " Tadeusz Struk
2022-03-11 1:49 ` Willem de Bruijn
2022-03-11 3:43 ` Tadeusz Struk
2022-03-12 1:40 ` patchwork-bot+netdevbpf
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