CVE-2023-53500

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

xfrm: fix slab-use-after-free in decode_session6

When the xfrm device is set to the qdisc of the sfb type, the cb field

of the sent skb may be modified during enqueuing. Then,

slab-use-after-free may occur when the xfrm device sends IPv6 packets.

The stack information is as follows:

BUG: KASAN: slab-use-after-free in decode_session6+0x103f/0x1890

Read of size 1 at addr ffff8881111458ef by task swapper/3/0

CPU: 3 PID: 0 Comm: swapper/3 Not tainted 6.4.0-next-20230707 #409

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.14.0-1.fc33 04/01/2014

Call Trace:

<IRQ>

dump_stack_lvl+0xd9/0x150

print_address_description.constprop.0+0x2c/0x3c0

kasan_report+0x11d/0x130

decode_session6+0x103f/0x1890

__xfrm_decode_session+0x54/0xb0

xfrmi_xmit+0x173/0x1ca0

dev_hard_start_xmit+0x187/0x700

sch_direct_xmit+0x1a3/0xc30

__qdisc_run+0x510/0x17a0

__dev_queue_xmit+0x2215/0x3b10

neigh_connected_output+0x3c2/0x550

ip6_finish_output2+0x55a/0x1550

ip6_finish_output+0x6b9/0x1270

ip6_output+0x1f1/0x540

ndisc_send_skb+0xa63/0x1890

ndisc_send_rs+0x132/0x6f0

addrconf_rs_timer+0x3f1/0x870

call_timer_fn+0x1a0/0x580

expire_timers+0x29b/0x4b0

run_timer_softirq+0x326/0x910

__do_softirq+0x1d4/0x905

irq_exit_rcu+0xb7/0x120

sysvec_apic_timer_interrupt+0x97/0xc0

</IRQ>

<TASK>

asm_sysvec_apic_timer_interrupt+0x1a/0x20

RIP: 0010:intel_idle_hlt+0x23/0x30

Code: 1f 84 00 00 00 00 00 f3 0f 1e fa 41 54 41 89 d4 0f 1f 44 00 00 66 90 0f 1f 44 00 00 0f 00 2d c4 9f ab 00 0f 1f 44 00 00 fb f4 <fa> 44 89 e0 41 5c c3 66 0f 1f 44 00 00 f3 0f 1e fa 41 54 41 89 d4

RSP: 0018:ffffc90000197d78 EFLAGS: 00000246

RAX: 00000000000a83c3 RBX: ffffe8ffffd09c50 RCX: ffffffff8a22d8e5

RDX: 0000000000000001 RSI: ffffffff8d3f8080 RDI: ffffe8ffffd09c50

RBP: ffffffff8d3f8080 R08: 0000000000000001 R09: ffffed1026ba6d9d

R10: ffff888135d36ceb R11: 0000000000000001 R12: 0000000000000001

R13: ffffffff8d3f8100 R14: 0000000000000001 R15: 0000000000000000

cpuidle_enter_state+0xd3/0x6f0

cpuidle_enter+0x4e/0xa0

do_idle+0x2fe/0x3c0

cpu_startup_entry+0x18/0x20

start_secondary+0x200/0x290

secondary_startup_64_no_verify+0x167/0x16b

</TASK>

Allocated by task 939:

kasan_save_stack+0x22/0x40

kasan_set_track+0x25/0x30

__kasan_slab_alloc+0x7f/0x90

kmem_cache_alloc_node+0x1cd/0x410

kmalloc_reserve+0x165/0x270

__alloc_skb+0x129/0x330

inet6_ifa_notify+0x118/0x230

__ipv6_ifa_notify+0x177/0xbe0

addrconf_dad_completed+0x133/0xe00

addrconf_dad_work+0x764/0x1390

process_one_work+0xa32/0x16f0

worker_thread+0x67d/0x10c0

kthread+0x344/0x440

ret_from_fork+0x1f/0x30

The buggy address belongs to the object at ffff888111145800

which belongs to the cache skbuff_small_head of size 640

The buggy address is located 239 bytes inside of

freed 640-byte region [ffff888111145800, ffff888111145a80)

As commit f855691975bb ("xfrm6: Fix the nexthdr offset in

_decode_session6.") showed, xfrm_decode_session was originally intended

only for the receive path. IP6CB(skb)->nhoff is not set during

transmission. Therefore, set the cb field in the skb to 0 before

sending packets.