[PATCH v2] net ticp:fix a kernel-infoleak in __tipc_sendmsg()

[tcs.kernel@gmail.com]

From: Haimin Zhang <tcs_kernel@tencent.com>

struct tipc_socket_addr.ref has a 4-byte hole,and __tipc_getname() currently
copying it to user space,causing kernel-infoleak.

BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:121 [inline]
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:121 [inline] lib/usercopy.c:33
BUG: KMSAN: kernel-infoleak in _copy_to_user+0x1c9/0x270 lib/usercopy.c:33 lib/usercopy.c:33
 instrument_copy_to_user include/linux/instrumented.h:121 [inline]
 instrument_copy_to_user include/linux/instrumented.h:121 [inline] lib/usercopy.c:33
 _copy_to_user+0x1c9/0x270 lib/usercopy.c:33 lib/usercopy.c:33
 copy_to_user include/linux/uaccess.h:209 [inline]
 copy_to_user include/linux/uaccess.h:209 [inline] net/socket.c:287
 move_addr_to_user+0x3f6/0x600 net/socket.c:287 net/socket.c:287
 __sys_getpeername+0x470/0x6b0 net/socket.c:1987 net/socket.c:1987
 __do_sys_getpeername net/socket.c:1997 [inline]
 __se_sys_getpeername net/socket.c:1994 [inline]
 __do_sys_getpeername net/socket.c:1997 [inline] net/socket.c:1994
 __se_sys_getpeername net/socket.c:1994 [inline] net/socket.c:1994
 __x64_sys_getpeername+0xda/0x120 net/socket.c:1994 net/socket.c:1994
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_x64 arch/x86/entry/common.c:51 [inline] arch/x86/entry/common.c:82
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Uninit was stored to memory at:
 tipc_getname+0x575/0x5e0 net/tipc/socket.c:757 net/tipc/socket.c:757
 __sys_getpeername+0x3b3/0x6b0 net/socket.c:1984 net/socket.c:1984
 __do_sys_getpeername net/socket.c:1997 [inline]
 __se_sys_getpeername net/socket.c:1994 [inline]
 __do_sys_getpeername net/socket.c:1997 [inline] net/socket.c:1994
 __se_sys_getpeername net/socket.c:1994 [inline] net/socket.c:1994
 __x64_sys_getpeername+0xda/0x120 net/socket.c:1994 net/socket.c:1994
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_x64 arch/x86/entry/common.c:51 [inline] arch/x86/entry/common.c:82
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Uninit was stored to memory at:
 msg_set_word net/tipc/msg.h:212 [inline]
 msg_set_destport net/tipc/msg.h:619 [inline]
 msg_set_word net/tipc/msg.h:212 [inline] net/tipc/socket.c:1486
 msg_set_destport net/tipc/msg.h:619 [inline] net/tipc/socket.c:1486
 __tipc_sendmsg+0x44fa/0x5890 net/tipc/socket.c:1486 net/tipc/socket.c:1486
 tipc_sendmsg+0xeb/0x140 net/tipc/socket.c:1402 net/tipc/socket.c:1402
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg net/socket.c:724 [inline]
 sock_sendmsg_nosec net/socket.c:704 [inline] net/socket.c:2409
 sock_sendmsg net/socket.c:724 [inline] net/socket.c:2409
 ____sys_sendmsg+0xe11/0x12c0 net/socket.c:2409 net/socket.c:2409
 ___sys_sendmsg net/socket.c:2463 [inline]
 ___sys_sendmsg net/socket.c:2463 [inline] net/socket.c:2492
 __sys_sendmsg+0x704/0x840 net/socket.c:2492 net/socket.c:2492
 __do_sys_sendmsg net/socket.c:2501 [inline]
 __se_sys_sendmsg net/socket.c:2499 [inline]
 __do_sys_sendmsg net/socket.c:2501 [inline] net/socket.c:2499
 __se_sys_sendmsg net/socket.c:2499 [inline] net/socket.c:2499
 __x64_sys_sendmsg+0xe2/0x120 net/socket.c:2499 net/socket.c:2499
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_x64 arch/x86/entry/common.c:51 [inline] arch/x86/entry/common.c:82
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Local variable skaddr created at:
 __tipc_sendmsg+0x2d0/0x5890 net/tipc/socket.c:1419 net/tipc/socket.c:1419
 tipc_sendmsg+0xeb/0x140 net/tipc/socket.c:1402 net/tipc/socket.c:1402

Bytes 4-7 of 16 are uninitialized
Memory access of size 16 starts at ffff888113753e00
Data copied to user address 0000000020000280

Reported-by: syzbot+cdbd40e0c3ca02cae3b7@syzkaller.appspotmail.com
Signed-off-by: Haimin Zhang <tcs_kernel@tencent.com>
Acked-by: Jon Maloy <jmaloy@redhat.com>
---
 net/tipc/socket.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/tipc/socket.c b/net/tipc/socket.c
index ad570c2..3e63c83 100644
--- a/net/tipc/socket.c
+++ b/net/tipc/socket.c
@@ -1461,6 +1461,8 @@ static int __tipc_sendmsg(struct socket *sock, struct msghdr *m, size_t dlen)
 		msg_set_syn(hdr, 1);
 	}
 
+	memset(&skaddr, 0, sizeof(skaddr));
+
 	/* Determine destination */
 	if (atype == TIPC_SERVICE_RANGE) {
 		return tipc_sendmcast(sock, ua, m, dlen, timeout);
-- 
1.8.3.1