Re: [PATCH linux-next] vpda: correctly size vdpa_nl_policy

From: "Michael S. Tsirkin" <mst@redhat.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: linux-kernel <linux-kernel@vger.kernel.org>,
	Eric Dumazet <edumazet@google.com>,
	syzbot <syzkaller@googlegroups.com>,
	Parav Pandit <parav@nvidia.com>, Eli Cohen <elic@nvidia.com>,
	Jason Wang <jasowang@redhat.com>
Subject: Re: [PATCH linux-next] vpda: correctly size vdpa_nl_policy
Date: Wed, 10 Feb 2021 16:26:17 -0500	[thread overview]
Message-ID: <20210210162559-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <20210210134911.4119555-1-eric.dumazet@gmail.com>

On Wed, Feb 10, 2021 at 05:49:11AM -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> We need to ensure last entry of vdpa_nl_policy[]
> is zero, otherwise out-of-bounds access is hurting us.
> 
> BUG: KASAN: global-out-of-bounds in netlink_policy_dump_add_policy+0x3b6/0x440   net/netlink/policy.c:160
> Read of size 1 at addr ffffffff89cc61d0 by task syz-executor181/8413
> 
> CPU: 0 PID: 8413 Comm: syz-executor181 Not tainted 5.11.0-rc6-next-20210205-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack   lib/dump_stack.c:79 [inline]
>  dump_stack+0x107/0x163   lib/dump_stack.c:120
>  print_address_description.constprop.0.cold+0x5/0x2f8   mm/kasan/report.c:232
>  __kasan_report   mm/kasan/report.c:399 [inline]
>  kasan_report.cold+0x7c/0xd8   mm/kasan/report.c:416
>  netlink_policy_dump_add_policy+0x3b6/0x440   net/netlink/policy.c:160
>  ctrl_dumppolicy_start+0x3e1/0x760   net/netlink/genetlink.c:1181
>  genl_start+0x3cc/0x670   net/netlink/genetlink.c:604
>  __netlink_dump_start+0x584/0x900   net/netlink/af_netlink.c:2363
>  genl_family_rcv_msg_dumpit+0x2af/0x310   net/netlink/genetlink.c:686
>  genl_family_rcv_msg   net/netlink/genetlink.c:780 [inline]
>  genl_rcv_msg+0x434/0x580   net/netlink/genetlink.c:800
>  netlink_rcv_skb+0x153/0x420   net/netlink/af_netlink.c:2494
>  genl_rcv+0x24/0x40   net/netlink/genetlink.c:811
>  netlink_unicast_kernel   net/netlink/af_netlink.c:1304 [inline]
>  netlink_unicast+0x533/0x7d0   net/netlink/af_netlink.c:1330
>  netlink_sendmsg+0x856/0xd90   net/netlink/af_netlink.c:1919
>  sock_sendmsg_nosec   net/socket.c:654 [inline]
>  sock_sendmsg+0xcf/0x120   net/socket.c:674
>  ____sys_sendmsg+0x6e8/0x810   net/socket.c:2350
>  ___sys_sendmsg+0xf3/0x170   net/socket.c:2404
>  __sys_sendmsg+0xe5/0x1b0   net/socket.c:2437
>  do_syscall_64+0x2d/0x70   arch/x86/entry/common.c:46
>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
> RIP: 0033:0x43ef29
> Code: 28 c3 e8 2a 14 00 00 66 2e 0f 1f 84 00 00 00 00 00 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
> RSP: 002b:00007ffc75c06108 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
> RAX: ffffffffffffffda RBX: 0000000000400488 RCX: 000000000043ef29
> RDX: 0000000000000000 RSI: 00000000200029c0 RDI: 0000000000000003
> RBP: 0000000000402f10 R08: 00000000004ac018 R09: 0000000000400488
> R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000402fa0
> R13: 0000000000000000 R14: 00000000004ac018 R15: 0000000000400488
> 
> The buggy address belongs to the variable:
>  vdpa_nl_policy+0x90/0x3a00
> 
> Memory state around the buggy address:
>  ffffffff89cc6080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>  ffffffff89cc6100: 00 00 00 00 f9 f9 f9 f9 00 00 00 00 00 00 00 00
> >ffffffff89cc6180: 00 00 00 00 00 00 00 00 00 00 f9 f9 f9 f9 f9 f9
>                                                  ^
>  ffffffff89cc6200: 05 f9 f9 f9 f9 f9 f9 f9 00 00 07 f9 f9 f9 f9 f9
>  ffffffff89cc6280: 00 00 00 01 f9 f9 f9 f9 00 07 f9 f9 f9 f9 f9 f9
> 
> Fixes: be7f5be9e84a ("vdpa: Define vdpa mgmt device, ops and a netlink interface")
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> Reported-by: syzbot <syzkaller@googlegroups.com>
> Cc: Parav Pandit <parav@nvidia.com>
> Cc: Eli Cohen <elic@nvidia.com>
> Cc: Jason Wang <jasowang@redhat.com>
> Cc: Michael S. Tsirkin <mst@redhat.com>

Oh good point, thanks!

Acked-by: Michael S. Tsirkin <mst@redhat.com>

> ---
>  drivers/vdpa/vdpa.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/vdpa/vdpa.c b/drivers/vdpa/vdpa.c
> index 9700a0adcca089fe9abb0b211fada314fa4a04ef..3d997b3893452f4da6a6800e128c57a9a024c0ad 100644
> --- a/drivers/vdpa/vdpa.c
> +++ b/drivers/vdpa/vdpa.c
> @@ -603,7 +603,7 @@ static int vdpa_nl_cmd_dev_get_dumpit(struct sk_buff *msg, struct netlink_callba
>  	return msg->len;
>  }
>  
> -static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX] = {
> +static const struct nla_policy vdpa_nl_policy[VDPA_ATTR_MAX + 1] = {
>  	[VDPA_ATTR_MGMTDEV_BUS_NAME] = { .type = NLA_NUL_STRING },
>  	[VDPA_ATTR_MGMTDEV_DEV_NAME] = { .type = NLA_STRING },
>  	[VDPA_ATTR_DEV_NAME] = { .type = NLA_STRING },
> -- 
> 2.30.0.478.g8a0d178c01-goog