Subject: CVE-2024-47707: ipv6: avoid possible NULL deref in rt6_uncached_list_flush_dev()

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

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

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

ipv6: avoid possible NULL deref in rt6_uncached_list_flush_dev()

Blamed commit accidentally removed a check for rt->rt6i_idev being NULL,
as spotted by syzbot:

Oops: general protection fault, probably for non-canonical address 0xdffffc0000000000: 0000 [#1] PREEMPT SMP KASAN PTI
KASAN: null-ptr-deref in range [0x0000000000000000-0x0000000000000007]
CPU: 1 UID: 0 PID: 10998 Comm: syz-executor Not tainted 6.11.0-rc6-syzkaller-00208-g625403177711 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
 RIP: 0010:rt6_uncached_list_flush_dev net/ipv6/route.c:177 [inline]
 RIP: 0010:rt6_disable_ip+0x33e/0x7e0 net/ipv6/route.c:4914
Code: 41 80 3c 04 00 74 0a e8 90 d0 9b f7 48 8b 7c 24 08 48 8b 07 48 89 44 24 10 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 f7 e8 64 d0 9b f7 48 8b 44 24 18 49 39 06
RSP: 0018:ffffc900047374e0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 1ffff1100fdf8f33 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff88807efc78c0
RBP: ffffc900047375d0 R08: 0000000000000003 R09: fffff520008e6e8c
R10: dffffc0000000000 R11: fffff520008e6e8c R12: 1ffff1100fdf8f18
R13: ffff88807efc7998 R14: 0000000000000000 R15: ffff88807efc7930
FS:  0000000000000000(0000) GS:ffff8880b8900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020002a80 CR3: 0000000022f62000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
 <TASK>
  addrconf_ifdown+0x15d/0x1bd0 net/ipv6/addrconf.c:3856
 addrconf_notify+0x3cb/0x1020
  notifier_call_chain+0x19f/0x3e0 kernel/notifier.c:93
  call_netdevice_notifiers_extack net/core/dev.c:2032 [inline]
  call_netdevice_notifiers net/core/dev.c:2046 [inline]
  unregister_netdevice_many_notify+0xd81/0x1c40 net/core/dev.c:11352
  unregister_netdevice_many net/core/dev.c:11414 [inline]
  unregister_netdevice_queue+0x303/0x370 net/core/dev.c:11289
  unregister_netdevice include/linux/netdevice.h:3129 [inline]
  __tun_detach+0x6b9/0x1600 drivers/net/tun.c:685
  tun_detach drivers/net/tun.c:701 [inline]
  tun_chr_close+0x108/0x1b0 drivers/net/tun.c:3510
  __fput+0x24a/0x8a0 fs/file_table.c:422
  task_work_run+0x24f/0x310 kernel/task_work.c:228
  exit_task_work include/linux/task_work.h:40 [inline]
  do_exit+0xa2f/0x27f0 kernel/exit.c:882
  do_group_exit+0x207/0x2c0 kernel/exit.c:1031
  __do_sys_exit_group kernel/exit.c:1042 [inline]
  __se_sys_exit_group kernel/exit.c:1040 [inline]
  __x64_sys_exit_group+0x3f/0x40 kernel/exit.c:1040
  x64_sys_call+0x2634/0x2640 arch/x86/include/generated/asm/syscalls_64.h:232
  do_syscall_x64 arch/x86/entry/common.c:52 [inline]
  do_syscall_64+0xf3/0x230 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7f1acc77def9
Code: Unable to access opcode bytes at 0x7f1acc77decf.
RSP: 002b:00007ffeb26fa738 EFLAGS: 00000246 ORIG_RAX: 00000000000000e7
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007f1acc77def9
RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000043
RBP: 00007f1acc7dd508 R08: 00007ffeb26f84d7 R09: 0000000000000003
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 0000000000000003 R14: 00000000ffffffff R15: 00007ffeb26fa8e0
 </TASK>
Modules linked in:
---[ end trace 0000000000000000 ]---
 RIP: 0010:rt6_uncached_list_flush_dev net/ipv6/route.c:177 [inline]
 RIP: 0010:rt6_disable_ip+0x33e/0x7e0 net/ipv6/route.c:4914
Code: 41 80 3c 04 00 74 0a e8 90 d0 9b f7 48 8b 7c 24 08 48 8b 07 48 89 44 24 10 4c 89 f0 48 c1 e8 03 48 b9 00 00 00 00 00 fc ff df <80> 3c 08 00 74 08 4c 89 f7 e8 64 d0 9b f7 48 8b 44 24 18 49 39 06
RSP: 0018:ffffc900047374e0 EFLAGS: 00010246
RAX: 0000000000000000 RBX: 1ffff1100fdf8f33 RCX: dffffc0000000000
RDX: 0000000000000000 RSI: 0000000000000004 RDI: ffff88807efc78c0
RBP: ffffc900047375d0 R08: 0000000000000003 R09: fffff520008e6e8c
R10: dffffc0000000000 R11: fffff520008e6e8c R12: 1ffff1100fdf8f18
R13: ffff88807efc7998 R14: 0000000000000000 R15: ffff88807efc7930
FS:  0000000000000000(0000) GS:ffff8880b8900000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020002a80 CR3: 0000000022f62000 CR4: 00000000003506f0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400

The Linux kernel CVE team has assigned CVE-2024-47707 to this issue.

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

	Issue introduced in 4.3 with commit e332bc67cf5e and fixed in 6.1.113 with commit f2bd9635543c
	Issue introduced in 4.3 with commit e332bc67cf5e and fixed in 6.6.54 with commit 0ceb2f2b5c81
	Issue introduced in 4.3 with commit e332bc67cf5e and fixed in 6.10.13 with commit 9a0ddc73be37
	Issue introduced in 4.3 with commit e332bc67cf5e and fixed in 6.11.2 with commit 08409e401622
	Issue introduced in 4.3 with commit e332bc67cf5e and fixed in 6.12-rc1 with commit 04ccecfa959d
	Issue introduced in 4.2.5 with commit 58d772c203ee

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-2024-47707
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/route.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/f2bd9635543ca41533b870f420872819f8331823
	https://git.kernel.org/stable/c/0ceb2f2b5c813f932d6e60d3feec5e7e713da783
	https://git.kernel.org/stable/c/9a0ddc73be37d19dff1ba08290af34e707d18e50
	https://git.kernel.org/stable/c/08409e401622e2896b4313be9f781bde8a2a6a53
	https://git.kernel.org/stable/c/04ccecfa959d3b9ae7348780d8e379c6486176ac