Subject: CVE-2024-47711: af_unix: Don't return OOB skb in manage_oob().

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

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

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

af_unix: Don't return OOB skb in manage_oob().

syzbot reported use-after-free in unix_stream_recv_urg(). [0]

The scenario is

  1. send(MSG_OOB)
  2. recv(MSG_OOB)
     -> The consumed OOB remains in recv queue
  3. send(MSG_OOB)
  4. recv()
     -> manage_oob() returns the next skb of the consumed OOB
     -> This is also OOB, but unix_sk(sk)->oob_skb is not cleared
  5. recv(MSG_OOB)
     -> unix_sk(sk)->oob_skb is used but already freed

The recent commit 8594d9b85c07 ("af_unix: Don't call skb_get() for OOB
skb.") uncovered the issue.

If the OOB skb is consumed and the next skb is peeked in manage_oob(),
we still need to check if the skb is OOB.

Let's do so by falling back to the following checks in manage_oob()
and add the test case in selftest.

Note that we need to add a similar check for SIOCATMARK.

[0]:
BUG: KASAN: slab-use-after-free in unix_stream_read_actor+0xa6/0xb0 net/unix/af_unix.c:2959
Read of size 4 at addr ffff8880326abcc4 by task syz-executor178/5235

CPU: 0 UID: 0 PID: 5235 Comm: syz-executor178 Not tainted 6.11.0-rc5-syzkaller-00742-gfbdaffe41adc #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
Call Trace:
 <TASK>
 __dump_stack lib/dump_stack.c:93 [inline]
 dump_stack_lvl+0x241/0x360 lib/dump_stack.c:119
 print_address_description mm/kasan/report.c:377 [inline]
 print_report+0x169/0x550 mm/kasan/report.c:488
 kasan_report+0x143/0x180 mm/kasan/report.c:601
 unix_stream_read_actor+0xa6/0xb0 net/unix/af_unix.c:2959
 unix_stream_recv_urg+0x1df/0x320 net/unix/af_unix.c:2640
 unix_stream_read_generic+0x2456/0x2520 net/unix/af_unix.c:2778
 unix_stream_recvmsg+0x22b/0x2c0 net/unix/af_unix.c:2996
 sock_recvmsg_nosec net/socket.c:1046 [inline]
 sock_recvmsg+0x22f/0x280 net/socket.c:1068
 ____sys_recvmsg+0x1db/0x470 net/socket.c:2816
 ___sys_recvmsg net/socket.c:2858 [inline]
 __sys_recvmsg+0x2f0/0x3e0 net/socket.c:2888
 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: 0033:0x7f5360d6b4e9
Code: 48 83 c4 28 c3 e8 37 17 00 00 0f 1f 80 00 00 00 00 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:00007fff29b3a458 EFLAGS: 00000246 ORIG_RAX: 000000000000002f
RAX: ffffffffffffffda RBX: 00007fff29b3a638 RCX: 00007f5360d6b4e9
RDX: 0000000000002001 RSI: 0000000020000640 RDI: 0000000000000003
RBP: 00007f5360dde610 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000000001
R13: 00007fff29b3a628 R14: 0000000000000001 R15: 0000000000000001
 </TASK>

Allocated by task 5235:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 unpoison_slab_object mm/kasan/common.c:312 [inline]
 __kasan_slab_alloc+0x66/0x80 mm/kasan/common.c:338
 kasan_slab_alloc include/linux/kasan.h:201 [inline]
 slab_post_alloc_hook mm/slub.c:3988 [inline]
 slab_alloc_node mm/slub.c:4037 [inline]
 kmem_cache_alloc_node_noprof+0x16b/0x320 mm/slub.c:4080
 __alloc_skb+0x1c3/0x440 net/core/skbuff.c:667
 alloc_skb include/linux/skbuff.h:1320 [inline]
 alloc_skb_with_frags+0xc3/0x770 net/core/skbuff.c:6528
 sock_alloc_send_pskb+0x91a/0xa60 net/core/sock.c:2815
 sock_alloc_send_skb include/net/sock.h:1778 [inline]
 queue_oob+0x108/0x680 net/unix/af_unix.c:2198
 unix_stream_sendmsg+0xd24/0xf80 net/unix/af_unix.c:2351
 sock_sendmsg_nosec net/socket.c:730 [inline]
 __sock_sendmsg+0x221/0x270 net/socket.c:745
 ____sys_sendmsg+0x525/0x7d0 net/socket.c:2597
 ___sys_sendmsg net/socket.c:2651 [inline]
 __sys_sendmsg+0x2b0/0x3a0 net/socket.c:2680
 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

Freed by task 5235:
 kasan_save_stack mm/kasan/common.c:47 [inline]
 kasan_save_track+0x3f/0x80 mm/kasan/common.c:68
 kasan_save_free_info+0x40/0x50 mm/kasan/generic.c:579
 poison_slab_object+0xe0/0x150 mm/kasan/common.c:240
 __kasan_slab_free+0x37/0x60 mm/kasan/common.c:256
 kasan_slab_free include/linux/kasan.h:184 [inline]
 slab_free_hook mm/slub.c:2252 [inline]
 slab_free mm/slub.c:4473 [inline]
 kmem_cache_free+0x145/0x350 mm/slub.c:4548
 unix_stream_read_generic+0x1ef6/0x2520 net/unix/af_unix.c:2917
 unix_stream_recvmsg+0x22b/0x2c0 net/unix/af_unix.c:2996
 sock_recvmsg_nosec net/socket.c:1046 [inline]
 sock_recvmsg+0x22f/0x280 net/socket.c:1068
 __sys_recvfrom+0x256/0x3e0 net/socket.c:2255
 __do_sys_recvfrom net/socket.c:2273 [inline]
 __se_sys_recvfrom net/socket.c:2269 [inline]
 __x64_sys_recvfrom+0xde/0x100 net/socket.c:2269
 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

The buggy address belongs to the object at ffff8880326abc80
 which belongs to the cache skbuff_head_cache of size 240
The buggy address is located 68 bytes inside of
 freed 240-byte region [ffff8880326abc80, ffff8880326abd70)

The buggy address belongs to the physical page:
page: refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x326ab
ksm flags: 0xfff00000000000(node=0|zone=1|lastcpupid=0x7ff)
page_type: 0xfdffffff(slab)
raw: 00fff00000000000 ffff88801eaee780 ffffea0000b7dc80 dead000000000003
raw: 0000000000000000 00000000800c000c 00000001fdffffff 0000000000000000
page dumped because: kasan: bad access detected
page_owner tracks the page as allocated
page last allocated via order 0, migratetype Unmovable, gfp_mask 0x52cc0(GFP_KERNEL|__GFP_NOWARN|__GFP_NORETRY|__GFP_COMP), pid 4686, tgid 4686 (udevadm), ts 32357469485, free_ts 28829011109
 set_page_owner include/linux/page_owner.h:32 [inline]
 post_alloc_hook+0x1f3/0x230 mm/page_alloc.c:1493
 prep_new_page mm/page_alloc.c:1501 [inline]
 get_page_from_freelist+0x2e4c/0x2f10 mm/page_alloc.c:3439
 __alloc_pages_noprof+0x256/0x6c0 mm/page_alloc.c:4695
 __alloc_pages_node_noprof include/linux/gfp.h:269 [inline]
 alloc_pages_node_noprof include/linux/gfp.h:296 [inline]
 alloc_slab_page+0x5f/0x120 mm/slub.c:2321
 allocate_slab+0x5a/0x2f0 mm/slub.c:2484
 new_slab mm/slub.c:2537 [inline]
 ___slab_alloc+0xcd1/0x14b0 mm/slub.c:3723
 __slab_alloc+0x58/0xa0 mm/slub.c:3813
 __slab_alloc_node mm/slub.c:3866 [inline]
 slab_alloc_node mm/slub.c:4025 [inline]
 kmem_cache_alloc_node_noprof+0x1fe/0x320 mm/slub.c:4080
 __alloc_skb+0x1c3/0x440 net/core/skbuff.c:667
 alloc_skb include/linux/skbuff.h:1320 [inline]
 alloc_uevent_skb+0x74/0x230 lib/kobject_uevent.c:289
 uevent_net_broadcast_untagged lib/kobject_uevent.c:326 [inline]
 kobject_uevent_net_broadcast+0x2fd/0x580 lib/kobject_uevent.c:410
 kobject_uevent_env+0x57d/0x8e0 lib/kobject_uevent.c:608
 kobject_synth_uevent+0x4ef/0xae0 lib/kobject_uevent.c:207
 uevent_store+0x4b/0x70 drivers/base/bus.c:633
 kernfs_fop_write_iter+0x3a1/0x500 fs/kernfs/file.c:334
 new_sync_write fs/read_write.c:497 [inline]
 vfs_write+0xa72/0xc90 fs/read_write.c:590
page last free pid 1 tgid 1 stack trace:
 reset_page_owner include/linux/page_owner.h:25 [inline]
 free_pages_prepare mm/page_alloc.c:1094 [inline]
 free_unref_page+0xd22/0xea0 mm/page_alloc.c:2612
 kasan_depopulate_vmalloc_pte+0x74/0x90 mm/kasan/shadow.c:408
 apply_to_pte_range mm/memory.c:2797 [inline]
 apply_to_pmd_range mm/memory.c:2841 [inline]
 apply_to_pud_range mm/memory.c:2877 [inline]
 apply_to_p4d_range mm/memory.c:2913 [inline]
 __apply_to_page_range+0x8a8/0xe50 mm/memory.c:2947
 kasan_release_vmalloc+0x9a/0xb0 mm/kasan/shadow.c:525
 purge_vmap_node+0x3e3/0x770 mm/vmalloc.c:2208
 __purge_vmap_area_lazy+0x708/0xae0 mm/vmalloc.c:2290
 _vm_unmap_aliases+0x79d/0x840 mm/vmalloc.c:2885
 change_page_attr_set_clr+0x2fe/0xdb0 arch/x86/mm/pat/set_memory.c:1881
 change_page_attr_set arch/x86/mm/pat/set_memory.c:1922 [inline]
 set_memory_nx+0xf2/0x130 arch/x86/mm/pat/set_memory.c:2110
 free_init_pages arch/x86/mm/init.c:924 [inline]
 free_kernel_image_pages arch/x86/mm/init.c:943 [inline]
 free_initmem+0x79/0x110 arch/x86/mm/init.c:970
 kernel_init+0x31/0x2b0 init/main.c:1476
 ret_from_fork+0x4b/0x80 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

Memory state around the buggy address:
 ffff8880326abb80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff8880326abc00: fb fb fb fb fb fb fc fc fc fc fc fc fc fc fc fc
>ffff8880326abc80: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                                           ^
 ffff8880326abd00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc
 ffff8880326abd80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb

The Linux kernel CVE team has assigned CVE-2024-47711 to this issue.

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

	Issue introduced in 6.10 with commit 93c99f21db36 and fixed in 6.11.2 with commit 4a7f9a2591a9
	Issue introduced in 6.10 with commit 93c99f21db36 and fixed in 6.12-rc1 with commit 5aa57d9f2d53
	Issue introduced in 6.9.8 with commit 71f8d9a4f6e0

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-2024-47711
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/unix/af_unix.c
	tools/testing/selftests/net/af_unix/msg_oob.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/4a7f9a2591a923bdde4bd7eac33490b6ae3b257c
	https://git.kernel.org/stable/c/5aa57d9f2d5311f19434d95b2a81610aa263e23b