CVE-2024-26608: ksmbd: fix global oob in ksmbd_nl_policy

[Lee Jones <lee@kernel.org>]

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

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

ksmbd: fix global oob in ksmbd_nl_policy

Similar to a reported issue (check the commit b33fb5b801c6 ("net:
qualcomm: rmnet: fix global oob in rmnet_policy"), my local fuzzer finds
another global out-of-bounds read for policy ksmbd_nl_policy. See bug
trace below:

==================================================================
BUG: KASAN: global-out-of-bounds in validate_nla lib/nlattr.c:386 [inline]
BUG: KASAN: global-out-of-bounds in __nla_validate_parse+0x24af/0x2750 lib/nlattr.c:600
Read of size 1 at addr ffffffff8f24b100 by task syz-executor.1/62810

CPU: 0 PID: 62810 Comm: syz-executor.1 Tainted: G                 N 6.1.0 #3
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.13.0-1ubuntu1.1 04/01/2014
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:88 [inline]
 dump_stack_lvl+0x8b/0xb3 lib/dump_stack.c:106
 print_address_description mm/kasan/report.c:284 [inline]
 print_report+0x172/0x475 mm/kasan/report.c:395
 kasan_report+0xbb/0x1c0 mm/kasan/report.c:495
 validate_nla lib/nlattr.c:386 [inline]
 __nla_validate_parse+0x24af/0x2750 lib/nlattr.c:600
 __nla_parse+0x3e/0x50 lib/nlattr.c:697
 __nlmsg_parse include/net/netlink.h:748 [inline]
 genl_family_rcv_msg_attrs_parse.constprop.0+0x1b0/0x290 net/netlink/genetlink.c:565
 genl_family_rcv_msg_doit+0xda/0x330 net/netlink/genetlink.c:734
 genl_family_rcv_msg net/netlink/genetlink.c:833 [inline]
 genl_rcv_msg+0x441/0x780 net/netlink/genetlink.c:850
 netlink_rcv_skb+0x14f/0x410 net/netlink/af_netlink.c:2540
 genl_rcv+0x24/0x40 net/netlink/genetlink.c:861
 netlink_unicast_kernel net/netlink/af_netlink.c:1319 [inline]
 netlink_unicast+0x54e/0x800 net/netlink/af_netlink.c:1345
 netlink_sendmsg+0x930/0xe50 net/netlink/af_netlink.c:1921
 sock_sendmsg_nosec net/socket.c:714 [inline]
 sock_sendmsg+0x154/0x190 net/socket.c:734
 ____sys_sendmsg+0x6df/0x840 net/socket.c:2482
 ___sys_sendmsg+0x110/0x1b0 net/socket.c:2536
 __sys_sendmsg+0xf3/0x1c0 net/socket.c:2565
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x3b/0x90 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7fdd66a8f359
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 f1 19 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 b8 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007fdd65e00168 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007fdd66bbcf80 RCX: 00007fdd66a8f359
RDX: 0000000000000000 RSI: 0000000020000500 RDI: 0000000000000003
RBP: 00007fdd66ada493 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 00007ffc84b81aff R14: 00007fdd65e00300 R15: 0000000000022000
 </TASK>

The buggy address belongs to the variable:
 ksmbd_nl_policy+0x100/0xa80

The buggy address belongs to the physical page:
page:0000000034f47940 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x1ccc4b
flags: 0x200000000001000(reserved|node=0|zone=2)
raw: 0200000000001000 ffffea00073312c8 ffffea00073312c8 0000000000000000
raw: 0000000000000000 0000000000000000 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffffffff8f24b000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffffffff8f24b080: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffffffff8f24b100: f9 f9 f9 f9 00 00 f9 f9 f9 f9 f9 f9 00 00 07 f9
                   ^
 ffffffff8f24b180: f9 f9 f9 f9 00 05 f9 f9 f9 f9 f9 f9 00 00 00 05
 ffffffff8f24b200: f9 f9 f9 f9 00 00 03 f9 f9 f9 f9 f9 00 00 04 f9
==================================================================

To fix it, add a placeholder named __KSMBD_EVENT_MAX and let
KSMBD_EVENT_MAX to be its original value - 1 according to what other
netlink families do. Also change two sites that refer the
KSMBD_EVENT_MAX to correct value.

The Linux kernel CVE team has assigned CVE-2024-26608 to this issue.


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

	Issue introduced in 5.15 with commit 0626e6641f6b and fixed in 5.15.149 with commit aaa1f1a2ee80
	Issue introduced in 5.15 with commit 0626e6641f6b and fixed in 6.1.76 with commit 2c939c74ef0b
	Issue introduced in 5.15 with commit 0626e6641f6b and fixed in 6.6.15 with commit 9863a53100f4
	Issue introduced in 5.15 with commit 0626e6641f6b and fixed in 6.7.3 with commit 6993328a4cd6
	Issue introduced in 5.15 with commit 0626e6641f6b and fixed in 6.8-rc2 with commit ebeae8adf89d

Please see https://www.kernel.org or 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-2024-26608
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:
	fs/smb/server/ksmbd_netlink.h
	fs/smb/server/transport_ipc.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/aaa1f1a2ee80888c12ae2783f3a0be10e14067c5
	https://git.kernel.org/stable/c/2c939c74ef0b74e99b92e32edc2a59f9b9ca3d5a
	https://git.kernel.org/stable/c/9863a53100f47652755545c2bd43e14a1855104d
	https://git.kernel.org/stable/c/6993328a4cd62a24df254b587c0796a4a1eecc95
	https://git.kernel.org/stable/c/ebeae8adf89d9a82359f6659b1663d09beec2faa