From dc56ad7028c5f559b3ce90d5cca2e6b7b839f1d5 Mon Sep 17 00:00:00 2001
From: Eric Dumazet <edumazet@google.com>
Date: Mon, 30 Aug 2021 10:21:37 -0700
Subject: [PATCH] af_unix: fix potential NULL deref in unix_dgram_connect()
Git-commit: dc56ad7028c5f559b3ce90d5cca2e6b7b839f1d5
References: git-fixes
Patch-mainline: v5.15-rc1
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>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
net/unix/af_unix.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 7cad52ba9cde..eb47b9de2380 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -495,7 +495,7 @@ 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)
@@ -1222,6 +1222,7 @@ 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
@@ -1235,7 +1236,10 @@ 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);
@@ -1248,8 +1252,6 @@ 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:
@@ -1831,6 +1833,7 @@ 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;
--
2.35.3