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[net-next] af_unix: fix potential NULL deref in unix_dgram_connect()

Message ID 20210830172137.325718-1-eric.dumazet@gmail.com (mailing list archive)
State Accepted
Commit dc56ad7028c5f559b3ce90d5cca2e6b7b839f1d5
Delegated to: Netdev Maintainers
Headers show
Series [net-next] af_unix: fix potential NULL deref in unix_dgram_connect() | expand

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netdev/source_inline success Was 0 now: 0
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netdev/module_param success Was 0 now: 0
netdev/build_32bit success Errors and warnings before: 4 this patch: 4
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netdev/checkpatch warning CHECK: multiple assignments should be avoided WARNING: Possible repeated word: 'Google'
netdev/build_allmodconfig_warn success Errors and warnings before: 4 this patch: 4
netdev/header_inline success Link

Commit Message

Eric Dumazet Aug. 30, 2021, 5:21 p.m. UTC 
From: Eric Dumazet <edumazet@google.com>

syzbot was able to trigger NULL deref in unix_dgram_connect() [1]

This happens in

	if (unix_peer(sk))
		sk->sk_state = other->sk_state = TCP_ESTABLISHED; // crash because @other is NULL

Because locks have been dropped, unix_peer() might be non NULL,
while @other is NULL (AF_UNSPEC case)

We need to move code around, so that we no longer access
unix_peer() and sk_state while locks have been released.

[1]
general protection fault, probably for non-canonical address 0xdffffc0000000002: 0000 [#1] PREEMPT SMP KASAN
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017]
CPU: 0 PID: 10341 Comm: syz-executor239 Not tainted 5.14.0-rc7-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
RIP: 0010:unix_dgram_connect+0x32a/0xc60 net/unix/af_unix.c:1226
Code: 00 00 45 31 ed 49 83 bc 24 f8 05 00 00 00 74 69 e8 eb 5b a6 f9 48 8d 7d 12 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 48 89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 e0 07 00 00
RSP: 0018:ffffc9000a89fcd8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000004 RCX: 0000000000000000
RDX: 0000000000000002 RSI: ffffffff87cf4ef5 RDI: 0000000000000012
RBP: 0000000000000000 R08: 0000000000000000 R09: ffff88802e1917c3
R10: ffffffff87cf4eba R11: 0000000000000001 R12: ffff88802e191740
R13: 0000000000000000 R14: ffff88802e191d38 R15: ffff88802e1917c0
FS:  00007f3eb0052700(0000) GS:ffff8880b9c00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000004787d0 CR3: 0000000029c0a000 CR4: 00000000001506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 __sys_connect_file+0x155/0x1a0 net/socket.c:1890
 __sys_connect+0x161/0x190 net/socket.c:1907
 __do_sys_connect net/socket.c:1917 [inline]
 __se_sys_connect net/socket.c:1914 [inline]
 __x64_sys_connect+0x6f/0xb0 net/socket.c:1914
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae
RIP: 0033:0x446a89
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 a1 15 00 00 90 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 bc ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f3eb0052208 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00000000004cc4d8 RCX: 0000000000446a89
RDX: 000000000000006e RSI: 0000000020000180 RDI: 0000000000000003
RBP: 00000000004cc4d0 R08: 00007f3eb0052700 R09: 0000000000000000
R10: 00007f3eb0052700 R11: 0000000000000246 R12: 00000000004cc4dc
R13: 00007ffd791e79cf R14: 00007f3eb0052300 R15: 0000000000022000
Modules linked in:
---[ end trace 4eb809357514968c ]---
RIP: 0010:unix_dgram_connect+0x32a/0xc60 net/unix/af_unix.c:1226
Code: 00 00 45 31 ed 49 83 bc 24 f8 05 00 00 00 74 69 e8 eb 5b a6 f9 48 8d 7d 12 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <0f> b6 04 02 48 89 fa 83 e2 07 38 d0 7f 08 84 c0 0f 85 e0 07 00 00
RSP: 0018:ffffc9000a89fcd8 EFLAGS: 00010202
RAX: dffffc0000000000 RBX: 0000000000000004 RCX: 0000000000000000
RDX: 0000000000000002 RSI: ffffffff87cf4ef5 RDI: 0000000000000012
RBP: 0000000000000000 R08: 0000000000000000 R09: ffff88802e1917c3
R10: ffffffff87cf4eba R11: 0000000000000001 R12: ffff88802e191740
R13: 0000000000000000 R14: ffff88802e191d38 R15: ffff88802e1917c0
FS:  00007f3eb0052700(0000) GS:ffff8880b9d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ffd791fe960 CR3: 0000000029c0a000 CR4: 00000000001506e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

Fixes: 83301b5367a9 ("af_unix: Set TCP_ESTABLISHED for datagram sockets too")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Cong Wang <cong.wang@bytedance.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Reported-by: syzbot <syzkaller@googlegroups.com>
---
 net/unix/af_unix.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Comments

patchwork-bot+netdevbpf@kernel.org Aug. 31, 2021, 11:10 a.m. UTC | #1 
Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Mon, 30 Aug 2021 10:21:37 -0700 you wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> syzbot was able to trigger NULL deref in unix_dgram_connect() [1]
> 
> This happens in
> 
> 	if (unix_peer(sk))
> 		sk->sk_state = other->sk_state = TCP_ESTABLISHED; // crash because @other is NULL
> 
> [...]

Here is the summary with links:
  - [net-next] af_unix: fix potential NULL deref in unix_dgram_connect()
    https://git.kernel.org/netdev/net-next/c/dc56ad7028c5

You are awesome, thank you!
--
Deet-doot-dot, I am a bot.
https://korg.docs.kernel.org/patchwork/pwbot.html
Cong Wang Aug. 31, 2021, 6:06 p.m. UTC | #2 
On Mon, Aug 30, 2021 at 10:21 AM Eric Dumazet <eric.dumazet@gmail.com> wrote:
> @@ -1805,6 +1807,7 @@ static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
>
>                         unix_state_unlock(sk);
>
> +                       sk->sk_state = TCP_CLOSE;

Does this need to be moved before the unix_state_unlock()?

The rest looks good to me.

Thanks.
diff mbox series

Patch

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 4cf0b1c47f0f99e99c12d37af2494f301a965856..5d49c92a2487d663d511d26c2cb024f5f3d670d8 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -494,7 +494,7 @@  static void unix_dgram_disconnected(struct sock *sk, struct sock *other)
 			sk_error_report(other);
 		}
 	}
-	sk->sk_state = other->sk_state = TCP_CLOSE;
+	other->sk_state = TCP_CLOSE;
 }
 
 static void unix_sock_destructor(struct sock *sk)
@@ -1196,6 +1196,7 @@  static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
 		if (err)
 			goto out_unlock;
 
+		sk->sk_state = other->sk_state = TCP_ESTABLISHED;
 	} else {
 		/*
 		 *	1003.1g breaking connected state with AF_UNSPEC
@@ -1209,7 +1210,10 @@  static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
 	 */
 	if (unix_peer(sk)) {
 		struct sock *old_peer = unix_peer(sk);
+
 		unix_peer(sk) = other;
+		if (!other)
+			sk->sk_state = TCP_CLOSE;
 		unix_dgram_peer_wake_disconnect_wakeup(sk, old_peer);
 
 		unix_state_double_unlock(sk, other);
@@ -1222,8 +1226,6 @@  static int unix_dgram_connect(struct socket *sock, struct sockaddr *addr,
 		unix_state_double_unlock(sk, other);
 	}
 
-	if (unix_peer(sk))
-		sk->sk_state = other->sk_state = TCP_ESTABLISHED;
 	return 0;
 
 out_unlock:
@@ -1805,6 +1807,7 @@  static int unix_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
 
 			unix_state_unlock(sk);
 
+			sk->sk_state = TCP_CLOSE;
 			unix_dgram_disconnected(sk, other);
 			sock_put(other);
 			err = -ECONNREFUSED;