Subject: CVE-2024-26852: net/ipv6: avoid possible UAF in ip6_route_mpath_notify()

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

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

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

net/ipv6: avoid possible UAF in ip6_route_mpath_notify()

syzbot found another use-after-free in ip6_route_mpath_notify() [1]

Commit f7225172f25a ("net/ipv6: prevent use after free in
ip6_route_mpath_notify") was not able to fix the root cause.

We need to defer the fib6_info_release() calls after
ip6_route_mpath_notify(), in the cleanup phase.

[1]
BUG: KASAN: slab-use-after-free in rt6_fill_node+0x1460/0x1ac0
Read of size 4 at addr ffff88809a07fc64 by task syz-executor.2/23037

CPU: 0 PID: 23037 Comm: syz-executor.2 Not tainted 6.8.0-rc4-syzkaller-01035-gea7f3cfaa588 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
Call Trace:
 <TASK>
  __dump_stack lib/dump_stack.c:88 [inline]
  dump_stack_lvl+0x1e7/0x2e0 lib/dump_stack.c:106
  print_address_description mm/kasan/report.c:377 [inline]
  print_report+0x167/0x540 mm/kasan/report.c:488
  kasan_report+0x142/0x180 mm/kasan/report.c:601
 rt6_fill_node+0x1460/0x1ac0
  inet6_rt_notify+0x13b/0x290 net/ipv6/route.c:6184
  ip6_route_mpath_notify net/ipv6/route.c:5198 [inline]
  ip6_route_multipath_add net/ipv6/route.c:5404 [inline]
  inet6_rtm_newroute+0x1d0f/0x2300 net/ipv6/route.c:5517
  rtnetlink_rcv_msg+0x885/0x1040 net/core/rtnetlink.c:6597
  netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2543
  netlink_unicast_kernel net/netlink/af_netlink.c:1341 [inline]
  netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1367
  netlink_sendmsg+0xa3b/0xd70 net/netlink/af_netlink.c:1908
  sock_sendmsg_nosec net/socket.c:730 [inline]
  __sock_sendmsg+0x221/0x270 net/socket.c:745
  ____sys_sendmsg+0x525/0x7d0 net/socket.c:2584
  ___sys_sendmsg net/socket.c:2638 [inline]
  __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2667
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77
RIP: 0033:0x7f73dd87dda9
Code: 28 00 00 00 75 05 48 83 c4 28 c3 e8 e1 20 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 b0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007f73de6550c8 EFLAGS: 00000246 ORIG_RAX: 000000000000002e
RAX: ffffffffffffffda RBX: 00007f73dd9ac050 RCX: 00007f73dd87dda9
RDX: 0000000000000000 RSI: 0000000020000140 RDI: 0000000000000005
RBP: 00007f73dd8ca47a R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000000
R13: 000000000000006e R14: 00007f73dd9ac050 R15: 00007ffdbdeb7858
 </TASK>

Allocated by task 23037:
  kasan_save_stack mm/kasan/common.c:47 [inline]
  kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
  poison_kmalloc_redzone mm/kasan/common.c:372 [inline]
  __kasan_kmalloc+0x98/0xb0 mm/kasan/common.c:389
  kasan_kmalloc include/linux/kasan.h:211 [inline]
  __do_kmalloc_node mm/slub.c:3981 [inline]
  __kmalloc+0x22e/0x490 mm/slub.c:3994
  kmalloc include/linux/slab.h:594 [inline]
  kzalloc include/linux/slab.h:711 [inline]
  fib6_info_alloc+0x2e/0xf0 net/ipv6/ip6_fib.c:155
  ip6_route_info_create+0x445/0x12b0 net/ipv6/route.c:3758
  ip6_route_multipath_add net/ipv6/route.c:5298 [inline]
  inet6_rtm_newroute+0x744/0x2300 net/ipv6/route.c:5517
  rtnetlink_rcv_msg+0x885/0x1040 net/core/rtnetlink.c:6597
  netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2543
  netlink_unicast_kernel net/netlink/af_netlink.c:1341 [inline]
  netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1367
  netlink_sendmsg+0xa3b/0xd70 net/netlink/af_netlink.c:1908
  sock_sendmsg_nosec net/socket.c:730 [inline]
  __sock_sendmsg+0x221/0x270 net/socket.c:745
  ____sys_sendmsg+0x525/0x7d0 net/socket.c:2584
  ___sys_sendmsg net/socket.c:2638 [inline]
  __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2667
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77

Freed by task 16:
  kasan_save_stack mm/kasan/common.c:47 [inline]
  kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
  kasan_save_free_info+0x4e/0x60 mm/kasan/generic.c:640
  poison_slab_object+0xa6/0xe0 mm/kasan/common.c:241
  __kasan_slab_free+0x34/0x70 mm/kasan/common.c:257
  kasan_slab_free include/linux/kasan.h:184 [inline]
  slab_free_hook mm/slub.c:2121 [inline]
  slab_free mm/slub.c:4299 [inline]
  kfree+0x14a/0x380 mm/slub.c:4409
  rcu_do_batch kernel/rcu/tree.c:2190 [inline]
  rcu_core+0xd76/0x1810 kernel/rcu/tree.c:2465
  __do_softirq+0x2bb/0x942 kernel/softirq.c:553

Last potentially related work creation:
  kasan_save_stack+0x3f/0x60 mm/kasan/common.c:47
  __kasan_record_aux_stack+0xae/0x100 mm/kasan/generic.c:586
  __call_rcu_common kernel/rcu/tree.c:2715 [inline]
  call_rcu+0x167/0xa80 kernel/rcu/tree.c:2829
  fib6_info_release include/net/ip6_fib.h:341 [inline]
  ip6_route_multipath_add net/ipv6/route.c:5344 [inline]
  inet6_rtm_newroute+0x114d/0x2300 net/ipv6/route.c:5517
  rtnetlink_rcv_msg+0x885/0x1040 net/core/rtnetlink.c:6597
  netlink_rcv_skb+0x1e3/0x430 net/netlink/af_netlink.c:2543
  netlink_unicast_kernel net/netlink/af_netlink.c:1341 [inline]
  netlink_unicast+0x7ea/0x980 net/netlink/af_netlink.c:1367
  netlink_sendmsg+0xa3b/0xd70 net/netlink/af_netlink.c:1908
  sock_sendmsg_nosec net/socket.c:730 [inline]
  __sock_sendmsg+0x221/0x270 net/socket.c:745
  ____sys_sendmsg+0x525/0x7d0 net/socket.c:2584
  ___sys_sendmsg net/socket.c:2638 [inline]
  __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2667
 do_syscall_64+0xf9/0x240
 entry_SYSCALL_64_after_hwframe+0x6f/0x77

The buggy address belongs to the object at ffff88809a07fc00
 which belongs to the cache kmalloc-512 of size 512
The buggy address is located 100 bytes inside of
 freed 512-byte region [ffff88809a07fc00, ffff88809a07fe00)

The buggy address belongs to the physical page:
page:ffffea0002681f00 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x9a07c
head:ffffea0002681f00 order:2 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0xfff00000000840(slab|head|node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xffffffff()
raw: 00fff00000000840 ffff888014c41c80 dead000000000122 0000000000000000
raw: 0000000000000000 0000000080100010 00000001ffffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 2, migratetype Unmovable, gfp_mask 0x1d20c0(__GFP_IO|__GFP_FS|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP|__GFP_NOMEMALLOC|__GFP_HARDWALL), pid 23028, tgid 23027 (syz-executor.4), ts 2340253595219, free_ts 2339107097036
  set_page_owner include/linux/page_owner.h:31 [inline]
  post_alloc_hook+0x1ea/0x210 mm/page_alloc.c:1533
  prep_new_page mm/page_alloc.c:1540 [inline]
  get_page_from_freelist+0x33ea/0x3580 mm/page_alloc.c:3311
  __alloc_pages+0x255/0x680 mm/page_alloc.c:4567
  __alloc_pages_node include/linux/gfp.h:238 [inline]
  alloc_pages_node include/linux/gfp.h:261 [inline]
  alloc_slab_page+0x5f/0x160 mm/slub.c:2190
  allocate_slab mm/slub.c:2354 [inline]
  new_slab+0x84/0x2f0 mm/slub.c:2407
  ___slab_alloc+0xd17/0x13e0 mm/slub.c:3540
  __slab_alloc mm/slub.c:3625 [inline]
  __slab_alloc_node mm/slub.c:3678 [inline]
  slab_alloc_node mm/slub.c:3850 [inline]
  __do_kmalloc_node mm/slub.c:3980 [inline]
  __kmalloc+0x2e0/0x490 mm/slub.c:3994
  kmalloc include/linux/slab.h:594 [inline]
  kzalloc include/linux/slab.h:711 [inline]
  new_dir fs/proc/proc_sysctl.c:956 [inline]
  get_subdir fs/proc/proc_sysctl.c:1000 [inline]
  sysctl_mkdir_p fs/proc/proc_sysctl.c:1295 [inline]
  __register_sysctl_table+0xb30/0x1440 fs/proc/proc_sysctl.c:1376
  neigh_sysctl_register+0x416/0x500 net/core/neighbour.c:3859
  devinet_sysctl_register+0xaf/0x1f0 net/ipv4/devinet.c:2644
  inetdev_init+0x296/0x4d0 net/ipv4/devinet.c:286
  inetdev_event+0x338/0x15c0 net/ipv4/devinet.c:1555
  notifier_call_chain+0x18f/0x3b0 kernel/notifier.c:93
  call_netdevice_notifiers_extack net/core/dev.c:1987 [inline]
  call_netdevice_notifiers net/core/dev.c:2001 [inline]
  register_netdevice+0x15b2/0x1a20 net/core/dev.c:10340
  br_dev_newlink+0x27/0x100 net/bridge/br_netlink.c:1563
  rtnl_newlink_create net/core/rtnetlink.c:3497 [inline]
  __rtnl_newlink net/core/rtnetlink.c:3717 [inline]
  rtnl_newlink+0x158f/0x20a0 net/core/rtnetlink.c:3730
page last free pid 11583 tgid 11583 stack trace:
  reset_page_owner include/linux/page_owner.h:24 [inline]
  free_pages_prepare mm/page_alloc.c:1140 [inline]
  free_unref_page_prepare+0x968/0xa90 mm/page_alloc.c:2346
  free_unref_page+0x37/0x3f0 mm/page_alloc.c:2486
  kasan_depopulate_vmalloc_pte+0x74/0x90 mm/kasan/shadow.c:415
  apply_to_pte_range mm/memory.c:2619 [inline]
  apply_to_pmd_range mm/memory.c:2663 [inline]
  apply_to_pud_range mm/memory.c:2699 [inline]
  apply_to_p4d_range mm/memory.c:2735 [inline]
  __apply_to_page_range+0x8ec/0xe40 mm/memory.c:2769
  kasan_release_vmalloc+0x9a/0xb0 mm/kasan/shadow.c:532
  __purge_vmap_area_lazy+0x163f/0x1a10 mm/vmalloc.c:1770
  drain_vmap_area_work+0x40/0xd0 mm/vmalloc.c:1804
  process_one_work kernel/workqueue.c:2633 [inline]
  process_scheduled_works+0x913/0x1420 kernel/workqueue.c:2706
  worker_thread+0xa5f/0x1000 kernel/workqueue.c:2787
  kthread+0x2ef/0x390 kernel/kthread.c:388
  ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
  ret_from_fork_asm+0x1b/0x30 arch/x86/entry/entry_64.S:242

Memory state around the buggy address:
 ffff88809a07fb00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
 ffff88809a07fb80: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
>ffff88809a07fc00: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                                       ^
 ffff88809a07fc80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff88809a07fd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb

The Linux kernel CVE team has assigned CVE-2024-26852 to this issue.

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

	Issue introduced in 4.11 with commit 3b1137fe7482 and fixed in 4.19.310 with commit 31ea5bcc7d4c
	Issue introduced in 4.11 with commit 3b1137fe7482 and fixed in 5.4.272 with commit 664f9c647260
	Issue introduced in 4.11 with commit 3b1137fe7482 and fixed in 5.10.213 with commit 79ce2e54cc0a
	Issue introduced in 4.11 with commit 3b1137fe7482 and fixed in 5.15.152 with commit cae330325795
	Issue introduced in 4.11 with commit 3b1137fe7482 and fixed in 6.1.82 with commit 394334fe2ae3
	Issue introduced in 4.11 with commit 3b1137fe7482 and fixed in 6.6.22 with commit ed883060c387
	Issue introduced in 4.11 with commit 3b1137fe7482 and fixed in 6.7.10 with commit 61b34f73cdbd
	Issue introduced in 4.11 with commit 3b1137fe7482 and fixed in 6.8 with commit 685f7d531264

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-2024-26852
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/31ea5bcc7d4cd1423de6be327a2c034725704136
	https://git.kernel.org/stable/c/664f9c647260cc9d68b4e31d9899530d89dd045e
	https://git.kernel.org/stable/c/79ce2e54cc0ae366f45516c00bf1b19aa43e9abe
	https://git.kernel.org/stable/c/cae3303257950d03ffec2df4a45e836f10d26c24
	https://git.kernel.org/stable/c/394334fe2ae3b9f1e2332b873857e84cb28aac18
	https://git.kernel.org/stable/c/ed883060c38721ed828061f6c0c30e5147326c9a
	https://git.kernel.org/stable/c/61b34f73cdbdb8eaf9ea12e9e2eb3b29716c4dda
	https://git.kernel.org/stable/c/685f7d531264599b3f167f1e94bbd22f120e5fab