Subject: CVE-2024-36901: ipv6: prevent NULL dereference in ip6_output()

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

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

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

ipv6: prevent NULL dereference in ip6_output()

According to syzbot, there is a chance that ip6_dst_idev()
returns NULL in ip6_output(). Most places in IPv6 stack
deal with a NULL idev just fine, but not here.

syzbot reported:

general protection fault, probably for non-canonical address 0xdffffc00000000bc: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x00000000000005e0-0x00000000000005e7]
CPU: 0 PID: 9775 Comm: syz-executor.4 Not tainted 6.9.0-rc5-syzkaller-00157-g6a30653b604a #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
 RIP: 0010:ip6_output+0x231/0x3f0 net/ipv6/ip6_output.c:237
Code: 3c 1e 00 49 89 df 74 08 4c 89 ef e8 19 58 db f7 48 8b 44 24 20 49 89 45 00 49 89 c5 48 8d 9d e0 05 00 00 48 89 d8 48 c1 e8 03 <42> 0f b6 04 38 84 c0 4c 8b 74 24 28 0f 85 61 01 00 00 8b 1b 31 ff
RSP: 0018:ffffc9000927f0d8 EFLAGS: 00010202
RAX: 00000000000000bc RBX: 00000000000005e0 RCX: 0000000000040000
RDX: ffffc900131f9000 RSI: 0000000000004f47 RDI: 0000000000004f48
RBP: 0000000000000000 R08: ffffffff8a1f0b9a R09: 1ffffffff1f51fad
R10: dffffc0000000000 R11: fffffbfff1f51fae R12: ffff8880293ec8c0
R13: ffff88805d7fc000 R14: 1ffff1100527d91a R15: dffffc0000000000
FS:  00007f135c6856c0(0000) GS:ffff8880b9400000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000080 CR3: 0000000064096000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  NF_HOOK include/linux/netfilter.h:314 [inline]
  ip6_xmit+0xefe/0x17f0 net/ipv6/ip6_output.c:358
  sctp_v6_xmit+0x9f2/0x13f0 net/sctp/ipv6.c:248
  sctp_packet_transmit+0x26ad/0x2ca0 net/sctp/output.c:653
  sctp_packet_singleton+0x22c/0x320 net/sctp/outqueue.c:783
  sctp_outq_flush_ctrl net/sctp/outqueue.c:914 [inline]
  sctp_outq_flush+0x6d5/0x3e20 net/sctp/outqueue.c:1212
  sctp_side_effects net/sctp/sm_sideeffect.c:1198 [inline]
  sctp_do_sm+0x59cc/0x60c0 net/sctp/sm_sideeffect.c:1169
  sctp_primitive_ASSOCIATE+0x95/0xc0 net/sctp/primitive.c:73
  __sctp_connect+0x9cd/0xe30 net/sctp/socket.c:1234
  sctp_connect net/sctp/socket.c:4819 [inline]
  sctp_inet_connect+0x149/0x1f0 net/sctp/socket.c:4834
  __sys_connect_file net/socket.c:2048 [inline]
  __sys_connect+0x2df/0x310 net/socket.c:2065
  __do_sys_connect net/socket.c:2075 [inline]
  __se_sys_connect net/socket.c:2072 [inline]
  __x64_sys_connect+0x7a/0x90 net/socket.c:2072
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf5/0x240 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

The Linux kernel CVE team has assigned CVE-2024-36901 to this issue.

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

	Issue introduced in 2.6.27 with commit 778d80be5269 and fixed in 5.10.222 with commit 9df3b2474a62
	Issue introduced in 2.6.27 with commit 778d80be5269 and fixed in 5.15.163 with commit 2272e2db38f2
	Issue introduced in 2.6.27 with commit 778d80be5269 and fixed in 6.1.91 with commit ea0cb87402f7
	Issue introduced in 2.6.27 with commit 778d80be5269 and fixed in 6.6.31 with commit e31b25cc2066
	Issue introduced in 2.6.27 with commit 778d80be5269 and fixed in 6.8.10 with commit 55f7eb4001ef
	Issue introduced in 2.6.27 with commit 778d80be5269 and fixed in 6.9 with commit 4db783d68b9b

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-2024-36901
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/ipv6/ip6_output.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/9df3b2474a627994433a87cbf325a562555b17de
	https://git.kernel.org/stable/c/2272e2db38f2e85929278146d7c770f22f528579
	https://git.kernel.org/stable/c/ea0cb87402f774b0e1214ffba0f57028b27cf155
	https://git.kernel.org/stable/c/e31b25cc2066d3f2b6c38579253882008d4469b0
	https://git.kernel.org/stable/c/55f7eb4001ef2a3b48cf039cf263f9ed0ec5a488
	https://git.kernel.org/stable/c/4db783d68b9b39a411a96096c10828ff5dfada7a