On Thu, May 22, 2025 at 3:31 PM Paul Moore [off-list ref] wrote:

quoted

On Thu, May 22, 2025 at 6:19 PM Kuniyuki Iwashima [off-list ref] wrote:

quoted

syzkaller reported a null-ptr-deref in txopt_get(). [0]

The offset 0x70 was of struct ipv6_txoptions in struct ipv6_pinfo,
so struct ipv6_pinfo was NULL there.

However, this never happens for IPv6 sockets as inet_sk(sk)->pinet6
is always set in inet6_create(), meaning the socket was not IPv6 one.

The root cause is missing validation in netlbl_conn_setattr().

netlbl_conn_setattr() switches branches based on struct
sockaddr.sa_family, which is passed from userspace.  However,
netlbl_conn_setattr() does not check if the address family matches
the socket.

The syzkaller must have called connect() for an IPv6 address on
an IPv4 socket.

We have a proper validation in tcp_v[46]_connect(), but
security_socket_connect() is called in the earlier stage.

Let's copy the validation to netlbl_conn_setattr().

[0]:
Oops: general protection fault, probably for non-canonical address 
0xdffffc000000000e: 0000 [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000070-0x0000000000000077]
CPU: 2 UID: 0 PID: 12928 Comm: syz.9.1677 Not tainted 6.12.0 #1
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.15.0-1 04/01/2014
RIP: 0010:txopt_get include/net/ipv6.h:390 [inline]
RIP: 0010:
Code: 02 00 00 49 8b ac 24 f8 02 00 00 e8 84 69 2a fd e8 ff 00 16 fd 48 8d 
7d 70 48 b8 00 00 00 00 00 fc ff df 48 89 fa 48 c1 ea 03 <80> 3c 02 00 0f 
85 53 02 00 00 48 8b 6d 70 48 85 ed 0f 84 ab 01 00
RSP: 0018:ffff88811b8afc48 EFLAGS: 00010212
RAX: dffffc0000000000 RBX: 1ffff11023715f8a RCX: ffffffff841ab00c
RDX: 000000000000000e RSI: ffffc90007d9e000 RDI: 0000000000000070
RBP: 0000000000000000 R08: ffffed1023715f9d R09: ffffed1023715f9e
R10: ffffed1023715f9d R11: 0000000000000003 R12: ffff888123075f00
R13: ffff88810245bd80 R14: ffff888113646780 R15: ffff888100578a80
FS:  00007f9019bd7640(0000) GS:ffff8882d2d00000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007f901b927bac CR3: 0000000104788003 CR4: 0000000000770ef0
PKRU: 80000000
Call Trace:
<TASK>
calipso_sock_setattr+0x56/0x80 net/netlabel/netlabel_calipso.c:557
netlbl_conn_setattr+0x10c/0x280 net/netlabel/netlabel_kapi.c:1177
selinux_netlbl_socket_connect_helper+0xd3/0x1b0 security/selinux/netlabel.c:569
selinux_netlbl_socket_connect_locked security/selinux/netlabel.c:597 [inline]
selinux_netlbl_socket_connect+0xb6/0x100 security/selinux/netlabel.c:615
selinux_socket_connect+0x5f/0x80 security/selinux/hooks.c:4931
security_socket_connect+0x50/0xa0 security/security.c:4598
__sys_connect_file+0xa4/0x190 net/socket.c:2067
__sys_connect+0x12c/0x170 net/socket.c:2088
__do_sys_connect net/socket.c:2098 [inline]
__se_sys_connect net/socket.c:2095 [inline]
__x64_sys_connect+0x73/0xb0 net/socket.c:2095
do_syscall_x64 arch/x86/entry/common.c:52 [inline]
do_syscall_64+0xaa/0x1b0 arch/x86/entry/common.c:83
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f901b61a12d
Code: 02 b8 ff ff ff ff c3 66 0f 1f 44 00 00 f3 0f 1e fa 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 a8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f9019bd6fa8 EFLAGS: 00000246 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 00007f901b925fa0 RCX: 00007f901b61a12d
RDX: 000000000000001c RSI: 0000200000000140 RDI: 0000000000000003
RBP: 00007f901b701505 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 0000000000000000 R14: 00007f901b5b62a0 R15: 00007f9019bb7000
</TASK>
Modules linked in:

Fixes: ceba1832b1b2 ("calipso: Set the calipso socket label to match the 
secattr.")
Reported-by: syzkaller <redacted>
Reported-by: John Cheung <redacted>
Closes: 
https://lore.kernel.org/netdev/CAP=Rh=M1LzunrcQB1fSGauMrJrhL6GGps5cPAKzHJXj6GQV+-g@mail.gmail.com/ (local)
Signed-off-by: Kuniyuki Iwashima <redacted>
---
net/netlabel/netlabel_kapi.c | 3 +++
1 file changed, 3 insertions(+)

Looks good to me, thanks for tracking this down and fixing it :)

Acked-by: Paul Moore <paul@paul-moore.com>

quoted

diff --git a/net/netlabel/netlabel_kapi.c b/net/netlabel/netlabel_kapi.c
index cd9160bbc919..6ea16138582c 100644
--- a/net/netlabel/netlabel_kapi.c
+++ b/net/netlabel/netlabel_kapi.c

@@ -1165,6 +1165,9 @@ int netlbl_conn_setattr(struct sock *sk,
         break;

#if IS_ENABLED(CONFIG_IPV6)
 case AF_INET6:
+               if (sk->sk_family != AF_INET6)
+                       return -EAFNOSUPPORT;

A more correct fix would be to not return with rcu_read_lock() held :/

I will send this :

diff --git a/net/netlabel/netlabel_kapi.c b/net/netlabel/netlabel_kapi.c

index 
6ea16138582c0b6ad39608f2c08bdfde7493a13e..33b77084a4e5f34770f960d7c82e481d9889753a
100644

--- a/net/netlabel/netlabel_kapi.c
+++ b/net/netlabel/netlabel_kapi.c

@@ -1165,8 +1165,10 @@ int netlbl_conn_setattr(struct sock *sk,
               break;

#if IS_ENABLED(CONFIG_IPV6)
       case AF_INET6:
-               if (sk->sk_family != AF_INET6)
-                       return -EAFNOSUPPORT;
+               if (sk->sk_family != AF_INET6) {
+                       ret_val = -EAFNOSUPPORT;
+                       goto conn_setattr_return;
+               }

               addr6 = (struct sockaddr_in6 *)addr;
               entry = netlbl_domhsh_getentry_af6(secattr->domain,