general protection fault in dccp_timeout_nlattr_to_obj

general protection fault in dccp_timeout_nlattr_to_obj

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit:    d89091a4 macb: Don't unregister clks unconditionally
git tree:       net
console output: https://syzkaller.appspot.com/x/log.txt?x=11b98466e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f2f3ef188b7e16cf
dashboard link: https://syzkaller.appspot.com/bug?extid=46a4ad33f345d1dd346e
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12ff2869e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16693751e00000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+46a4ad33f345d1dd346e@syzkaller.appspotmail.com

netlink: 24 bytes leftover after parsing attributes in process  
`syz-executor813'.
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: 0 PID: 9522 Comm: syz-executor813 Not tainted 5.5.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
RIP: 0010:dccp_timeout_nlattr_to_obj+0x60/0x230  
net/netfilter/nf_conntrack_proto_dccp.c:682
Code: 89 d8 48 c1 e8 03 42 0f b6 14 30 48 89 d8 83 e0 07 83 c0 03 38 d0 7c  
08 84 d2 0f 85 a1 01 00 00 4c 89 e0 44 8b 3b 48 c1 e8 03 <42> 0f b6 14 30  
4c 89 e0 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85
RSP: 0018:ffffc90001fd73d8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff8a4cd6fc RCX: ffffffff866323e9
RDX: 0000000000000000 RSI: ffffffff866117d5 RDI: ffff888098c2cf00
RBP: ffffc90001fd7418 R08: ffff88809f51c280 R09: ffff888098c2cf00
R10: ffffed10131859e7 R11: ffff888098c2cf3f R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000005dc0
FS:  00000000022f4880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000200 CR3: 00000000a6a68000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
  ctnl_timeout_parse_policy+0x150/0x1d0  
net/netfilter/nfnetlink_cttimeout.c:67
  cttimeout_default_set+0x150/0x1c0 net/netfilter/nfnetlink_cttimeout.c:368
  nfnetlink_rcv_msg+0xcf2/0xfb0 net/netfilter/nfnetlink.c:229
  netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477
  nfnetlink_rcv+0x1ba/0x460 net/netfilter/nfnetlink.c:563
  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: 0033:0x4401e9
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:00007ffe699346c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00000000004002c8 RCX: 00000000004401e9
RDX: 0000000000000940 RSI: 0000000020000200 RDI: 0000000000000003
RBP: 00000000006ca018 R08: 0000000000000000 R09: 00000000004002c8
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000401a70
R13: 0000000000401b00 R14: 0000000000000000 R15: 0000000000000000
Modules linked in:
---[ end trace 0b60d1e6ef381959 ]---
RIP: 0010:dccp_timeout_nlattr_to_obj+0x60/0x230  
net/netfilter/nf_conntrack_proto_dccp.c:682
Code: 89 d8 48 c1 e8 03 42 0f b6 14 30 48 89 d8 83 e0 07 83 c0 03 38 d0 7c  
08 84 d2 0f 85 a1 01 00 00 4c 89 e0 44 8b 3b 48 c1 e8 03 <42> 0f b6 14 30  
4c 89 e0 83 e0 07 83 c0 03 38 d0 7c 08 84 d2 0f 85
RSP: 0018:ffffc90001fd73d8 EFLAGS: 00010246
RAX: 0000000000000000 RBX: ffffffff8a4cd6fc RCX: ffffffff866323e9
RDX: 0000000000000000 RSI: ffffffff866117d5 RDI: ffff888098c2cf00
RBP: ffffc90001fd7418 R08: ffff88809f51c280 R09: ffff888098c2cf00
R10: ffffed10131859e7 R11: ffff888098c2cf3f R12: 0000000000000000
R13: 0000000000000000 R14: dffffc0000000000 R15: 0000000000005dc0
FS:  00000000022f4880(0000) GS:ffff8880ae800000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffffffffff600400 CR3: 00000000a6a68000 CR4: 00000000001406f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400


---
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[PATCH nf] netfilter: conntrack: dccp, sctp: handle null timeout argument

[Florian Westphal]

The timeout pointer can be NULL which means we should modify the
per-nets timeout instead.

All do this, except sctp and dccp which instead give:

general protection fault: 0000 [#1] PREEMPT SMP KASAN
net/netfilter/nf_conntrack_proto_dccp.c:682
 ctnl_timeout_parse_policy+0x150/0x1d0 net/netfilter/nfnetlink_cttimeout.c:67
 cttimeout_default_set+0x150/0x1c0 net/netfilter/nfnetlink_cttimeout.c:368
 nfnetlink_rcv_msg+0xcf2/0xfb0 net/netfilter/nfnetlink.c:229
 netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477

Reported-by: syzbot+46a4ad33f345d1dd346e@syzkaller.appspotmail.com
Fixes: c779e849608a8 ("netfilter: conntrack: remove get_timeout() indirection")
Signed-off-by: Florian Westphal <fw@strlen.de>
---
 net/netfilter/nf_conntrack_proto_dccp.c | 3 +++
 net/netfilter/nf_conntrack_proto_sctp.c | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/net/netfilter/nf_conntrack_proto_dccp.c b/net/netfilter/nf_conntrack_proto_dccp.c
index b6b14db3955b..b3f4a334f9d7 100644
--- a/net/netfilter/nf_conntrack_proto_dccp.c
+++ b/net/netfilter/nf_conntrack_proto_dccp.c
@@ -677,6 +677,9 @@ static int dccp_timeout_nlattr_to_obj(struct nlattr *tb[],
 	unsigned int *timeouts = data;
 	int i;
 
+	if (!timeouts)
+		 timeouts = dn->dccp_timeout;
+
 	/* set default DCCP timeouts. */
 	for (i=0; i<CT_DCCP_MAX; i++)
 		timeouts[i] = dn->dccp_timeout[i];
diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index fce3d93f1541..0399ae8f1188 100644
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -594,6 +594,9 @@ static int sctp_timeout_nlattr_to_obj(struct nlattr *tb[],
 	struct nf_sctp_net *sn = nf_sctp_pernet(net);
 	int i;
 
+	if (!timeouts)
+		timeouts = sn->timeouts;
+
 	/* set default SCTP timeouts. */
 	for (i=0; i<SCTP_CONNTRACK_MAX; i++)
 		timeouts[i] = sn->timeouts[i];
-- 
2.24.1

Re: general protection fault in dccp_timeout_nlattr_to_obj

[syzbot]

syzbot has bisected this bug to:

commit dd2934a95701576203b2f61e8ded4e4a2f9183ea
Author: Florian Westphal <fw@strlen.de>
Date:   Mon Sep 17 10:02:54 2018 +0000

     netfilter: conntrack: remove l3->l4 mapping information

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=10957485e00000
start commit:   d89091a4 macb: Don't unregister clks unconditionally
git tree:       net
final crash:    https://syzkaller.appspot.com/x/report.txt?x=12957485e00000
console output: https://syzkaller.appspot.com/x/log.txt?x=14957485e00000
kernel config:  https://syzkaller.appspot.com/x/.config?x=f2f3ef188b7e16cf
dashboard link: https://syzkaller.appspot.com/bug?extid=46a4ad33f345d1dd346e
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=12ff2869e00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=16693751e00000

Reported-by: syzbot+46a4ad33f345d1dd346e@syzkaller.appspotmail.com
Fixes: dd2934a95701 ("netfilter: conntrack: remove l3->l4 mapping  
information")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection

Re: [PATCH nf] netfilter: conntrack: dccp, sctp: handle null timeout argument

[Pablo Neira Ayuso]

On Mon, Jan 06, 2020 at 11:34:17PM +0100, Florian Westphal wrote:
> The timeout pointer can be NULL which means we should modify the
> per-nets timeout instead.
> 
> All do this, except sctp and dccp which instead give:
> 
> general protection fault: 0000 [#1] PREEMPT SMP KASAN
> net/netfilter/nf_conntrack_proto_dccp.c:682
>  ctnl_timeout_parse_policy+0x150/0x1d0 net/netfilter/nfnetlink_cttimeout.c:67
>  cttimeout_default_set+0x150/0x1c0 net/netfilter/nfnetlink_cttimeout.c:368
>  nfnetlink_rcv_msg+0xcf2/0xfb0 net/netfilter/nfnetlink.c:229
>  netlink_rcv_skb+0x177/0x450 net/netlink/af_netlink.c:2477

Applied, thanks Florian.