Subject: CVE-2021-47597: inet_diag: fix kernel-infoleak for UDP sockets

From: Greg Kroah-Hartman <[email-masked]>

Description
===========

In the Linux kernel, the following vulnerability has been resolved:

inet_diag: fix kernel-infoleak for UDP sockets

KMSAN reported a kernel-infoleak [1], that can exploited
by unpriv users.

After analysis it turned out UDP was not initializing
r->idiag_expires. Other users of inet_sk_diag_fill()
might make the same mistake in the future, so fix this
in inet_sk_diag_fill().

[1]
BUG: KMSAN: kernel-infoleak in instrument_copy_to_user include/linux/instrumented.h:121 [inline]
BUG: KMSAN: kernel-infoleak in copyout lib/iov_iter.c:156 [inline]
BUG: KMSAN: kernel-infoleak in _copy_to_iter+0x69d/0x25c0 lib/iov_iter.c:670
 instrument_copy_to_user include/linux/instrumented.h:121 [inline]
 copyout lib/iov_iter.c:156 [inline]
 _copy_to_iter+0x69d/0x25c0 lib/iov_iter.c:670
 copy_to_iter include/linux/uio.h:155 [inline]
 simple_copy_to_iter+0xf3/0x140 net/core/datagram.c:519
 __skb_datagram_iter+0x2cb/0x1280 net/core/datagram.c:425
 skb_copy_datagram_iter+0xdc/0x270 net/core/datagram.c:533
 skb_copy_datagram_msg include/linux/skbuff.h:3657 [inline]
 netlink_recvmsg+0x660/0x1c60 net/netlink/af_netlink.c:1974
 sock_recvmsg_nosec net/socket.c:944 [inline]
 sock_recvmsg net/socket.c:962 [inline]
 sock_read_iter+0x5a9/0x630 net/socket.c:1035
 call_read_iter include/linux/fs.h:2156 [inline]
 new_sync_read fs/read_write.c:400 [inline]
 vfs_read+0x1631/0x1980 fs/read_write.c:481
 ksys_read+0x28c/0x520 fs/read_write.c:619
 __do_sys_read fs/read_write.c:629 [inline]
 __se_sys_read fs/read_write.c:627 [inline]
 __x64_sys_read+0xdb/0x120 fs/read_write.c:627
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Uninit was created at:
 slab_post_alloc_hook mm/slab.h:524 [inline]
 slab_alloc_node mm/slub.c:3251 [inline]
 __kmalloc_node_track_caller+0xe0c/0x1510 mm/slub.c:4974
 kmalloc_reserve net/core/skbuff.c:354 [inline]
 __alloc_skb+0x545/0xf90 net/core/skbuff.c:426
 alloc_skb include/linux/skbuff.h:1126 [inline]
 netlink_dump+0x3d5/0x16a0 net/netlink/af_netlink.c:2245
 __netlink_dump_start+0xd1c/0xee0 net/netlink/af_netlink.c:2370
 netlink_dump_start include/linux/netlink.h:254 [inline]
 inet_diag_handler_cmd+0x2e7/0x400 net/ipv4/inet_diag.c:1343
 sock_diag_rcv_msg+0x24a/0x620
 netlink_rcv_skb+0x447/0x800 net/netlink/af_netlink.c:2491
 sock_diag_rcv+0x63/0x80 net/core/sock_diag.c:276
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x1095/0x1360 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x16f3/0x1870 net/netlink/af_netlink.c:1916
 sock_sendmsg_nosec net/socket.c:704 [inline]
 sock_sendmsg net/socket.c:724 [inline]
 sock_write_iter+0x594/0x690 net/socket.c:1057
 do_iter_readv_writev+0xa7f/0xc70
 do_iter_write+0x52c/0x1500 fs/read_write.c:851
 vfs_writev fs/read_write.c:924 [inline]
 do_writev+0x63f/0xe30 fs/read_write.c:967
 __do_sys_writev fs/read_write.c:1040 [inline]
 __se_sys_writev fs/read_write.c:1037 [inline]
 __x64_sys_writev+0xe5/0x120 fs/read_write.c:1037
 do_syscall_x64 arch/x86/entry/common.c:51 [inline]
 do_syscall_64+0x54/0xd0 arch/x86/entry/common.c:82
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Bytes 68-71 of 312 are uninitialized
Memory access of size 312 starts at ffff88812ab54000
Data copied to user address 0000000020001440

CPU: 1 PID: 6365 Comm: syz-executor801 Not tainted 5.16.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011

The Linux kernel CVE team has assigned CVE-2021-47597 to this issue.

Affected and fixed versions
===========================

	Issue introduced in 3.3 with commit 3c4d05c80567 and fixed in 5.4.168 with commit 7b5596e53125
	Issue introduced in 3.3 with commit 3c4d05c80567 and fixed in 5.10.88 with commit 3a4f6dba1eb9
	Issue introduced in 3.3 with commit 3c4d05c80567 and fixed in 5.15.11 with commit e5d28205bf1d
	Issue introduced in 3.3 with commit 3c4d05c80567 and fixed in 5.16 with commit 71ddeac8cd1d

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2021-47597
will be updated if fixes are backported, please check that for the most
up to date information about this issue.

Affected files
==============

The file(s) affected by this issue are:
	net/ipv4/inet_diag.c

Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/7b5596e531253ce84213d9daa7120b71c9d83198
	https://git.kernel.org/stable/c/3a4f6dba1eb98101abc012ef968a8b10dac1ce50
	https://git.kernel.org/stable/c/e5d28205bf1de7082d904ed277ceb2db2879e302
	https://git.kernel.org/stable/c/71ddeac8cd1d217744a0e060ff520e147c9328d1