general protection fault in nft_tunnel_get_init

general protection fault in nft_tunnel_get_init

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    51d69817 Merge tag 'platform-drivers-x86-v5.5-3' of git://..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1703533ee00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=d9290aeb7e6cf1c4
dashboard link: https://syzkaller.appspot.com/bug?extid=76d0b80493ac881ff77b
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=166f4bfee00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=159c4371e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+76d0b80493ac881ff77b@syzkaller.appspotmail.com

kasan: CONFIG_KASAN_INLINE enabled
kasan: GPF could be caused by NULL-ptr deref or user memory access
general protection fault: 0000 [#1] PREEMPT SMP KASAN
CPU: 1 PID: 9557 Comm: syz-executor096 Not tainted 5.5.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:nla_get_be32 include/net/netlink.h:1483 [inline]
RIP: 0010:nft_tunnel_get_init+0x65/0x2b0 net/netfilter/nft_tunnel.c:83
Code: 02 00 00 4c 8b 6b 08 4d 85 ed 0f 84 ba 01 00 00 e8 a0 8d 08 fb 49 8d  
7d 04 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48  
89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 df
RSP: 0018:ffffc90002127398 EFLAGS: 00010247
RAX: dffffc0000000000 RBX: ffff88808b620008 RCX: ffffffff866720af
RDX: 0000000000000000 RSI: ffffffff866c67e0 RDI: 0000000000000004
RBP: ffffc900021273c8 R08: ffff88809f4424c0 R09: ffffed1015d2703d
R10: ffffed1015d2703c R11: ffff8880ae9381e3 R12: ffff88809824ac18
R13: 0000000000000000 R14: 0000000000000000 R15: ffffc90002127498
FS:  00000000011dc880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200009c6 CR3: 00000000a8486000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  nf_tables_newexpr net/netfilter/nf_tables_api.c:2466 [inline]
  nf_tables_newrule+0xd96/0x2400 net/netfilter/nf_tables_api.c:3074
  nfnetlink_rcv_batch+0xf42/0x17a0 net/netfilter/nfnetlink.c:433
  nfnetlink_rcv_skb_batch net/netfilter/nfnetlink.c:543 [inline]
  nfnetlink_rcv+0x3e7/0x460 net/netfilter/nfnetlink.c:561
  netlink_unicast_kernel net/netlink/af_netlink.c:1302 [inline]
  netlink_unicast+0x58c/0x7d0 net/netlink/af_netlink.c:1328
  netlink_sendmsg+0x91c/0xea0 net/netlink/af_netlink.c:1917
  sock_sendmsg_nosec net/socket.c:639 [inline]
  sock_sendmsg+0xd7/0x130 net/socket.c:659
  ____sys_sendmsg+0x753/0x880 net/socket.c:2330
  ___sys_sendmsg+0x100/0x170 net/socket.c:2384
  __sys_sendmsg+0x105/0x1d0 net/socket.c:2417
  __do_sys_sendmsg net/socket.c:2426 [inline]
  __se_sys_sendmsg net/socket.c:2424 [inline]
  __x64_sys_sendmsg+0x78/0xb0 net/socket.c:2424
  do_syscall_64+0xfa/0x790 arch/x86/entry/common.c:294
  entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x4407b9
Code: 18 89 d0 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 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 0f 83 fb 13 fc ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007ffe11777578 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004407b9
RDX: 0000000000000000 RSI: 0000000020000240 RDI: 0000000000000004
RBP: 00000000006ca018 R08: 0000000000000001 R09: 00000000004002c8
R10: 0000000000000011 R11: 0000000000000246 R12: 0000000000402040
R13: 00000000004020d0 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace e202d5958993ae18 ]---
RIP: 0010:nla_get_be32 include/net/netlink.h:1483 [inline]
RIP: 0010:nft_tunnel_get_init+0x65/0x2b0 net/netfilter/nft_tunnel.c:83
Code: 02 00 00 4c 8b 6b 08 4d 85 ed 0f 84 ba 01 00 00 e8 a0 8d 08 fb 49 8d  
7d 04 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 14 02 48  
89 f8 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85 df
RSP: 0018:ffffc90002127398 EFLAGS: 00010247
RAX: dffffc0000000000 RBX: ffff88808b620008 RCX: ffffffff866720af
RDX: 0000000000000000 RSI: ffffffff866c67e0 RDI: 0000000000000004
RBP: ffffc900021273c8 R08: ffff88809f4424c0 R09: ffffed1015d2703d
R10: ffffed1015d2703c R11: ffff8880ae9381e3 R12: ffff88809824ac18
R13: 0000000000000000 R14: 0000000000000000 R15: ffffc90002127498
FS:  00000000011dc880(0000) GS:ffff8880ae900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000200009c6 CR3: 00000000a8486000 CR4: 00000000001406e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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[PATCH nf] netfilter: nft_tunnel: fix null-attribute check

[Florian Westphal]

else we get null deref when one of the attributes is missing, both
must be non-null.

Reported-by: syzbot+76d0b80493ac881ff77b@syzkaller.appspotmail.com
Fixes: aaecfdb5c5dd8ba ("netfilter: nf_tables: match on tunnel metadata")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nft_tunnel.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/netfilter/nft_tunnel.c b/net/netfilter/nft_tunnel.c
index 3d4c2ae605a8..d89c7c553030 100644
--- a/net/netfilter/nft_tunnel.c
+++ b/net/netfilter/nft_tunnel.c
@@ -76,7 +76,7 @@ static int nft_tunnel_get_init(const struct nft_ctx *ctx,
 	struct nft_tunnel *priv = nft_expr_priv(expr);
 	u32 len;
 
-	if (!tb[NFTA_TUNNEL_KEY] &&
+	if (!tb[NFTA_TUNNEL_KEY] ||
 	    !tb[NFTA_TUNNEL_DREG])
 		return -EINVAL;
 
-- 
2.24.1

Re: [PATCH nf] netfilter: nft_tunnel: fix null-attribute check

[Pablo Neira Ayuso]

On Thu, Jan 16, 2020 at 08:44:11AM +0100, Florian Westphal wrote:
> else we get null deref when one of the attributes is missing, both
> must be non-null.

Also applied, thanks.