xfrm: add NULL check in xfrm_update_ae_params

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

xfrm: add NULL check in xfrm_update_ae_params

Normally, x->replay_esn and x->preplay_esn should be allocated at

xfrm_alloc_replay_state_esn(...) in xfrm_state_construct(...), hence the

xfrm_update_ae_params(...) is okay to update them. However, the current

implementation of xfrm_new_ae(...) allows a malicious user to directly

dereference a NULL pointer and crash the kernel like below.

BUG: kernel NULL pointer dereference, address: 0000000000000000

PGD 8253067 P4D 8253067 PUD 8e0e067 PMD 0

Oops: 0002 [#1] PREEMPT SMP KASAN NOPTI

CPU: 0 PID: 98 Comm: poc.npd Not tainted 6.4.0-rc7-00072-gdad9774deaf1 #8

Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS rel-1.16.0-0-gd239552ce722-prebuilt.qemu.o4

RIP: 0010:memcpy_orig+0xad/0x140

Code: e8 4c 89 5f e0 48 8d 7f e0 73 d2 83 c2 20 48 29 d6 48 29 d7 83 fa 10 72 34 4c 8b 06 4c 8b 4e 08 c

RSP: 0018:ffff888008f57658 EFLAGS: 00000202

RAX: 0000000000000000 RBX: ffff888008bd0000 RCX: ffffffff8238e571

RDX: 0000000000000018 RSI: ffff888007f64844 RDI: 0000000000000000

RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000

R10: 0000000000000000 R11: 0000000000000000 R12: ffff888008f57818

R13: ffff888007f64aa4 R14: 0000000000000000 R15: 0000000000000000

FS: 00000000014013c0(0000) GS:ffff88806d600000(0000) knlGS:0000000000000000

CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033

CR2: 0000000000000000 CR3: 00000000054d8000 CR4: 00000000000006f0

Call Trace:

<TASK>

? __die+0x1f/0x70

? page_fault_oops+0x1e8/0x500

? __pfx_is_prefetch.constprop.0+0x10/0x10

? __pfx_page_fault_oops+0x10/0x10

? _raw_spin_unlock_irqrestore+0x11/0x40

? fixup_exception+0x36/0x460

? _raw_spin_unlock_irqrestore+0x11/0x40

? exc_page_fault+0x5e/0xc0

? asm_exc_page_fault+0x26/0x30

? xfrm_update_ae_params+0xd1/0x260

? memcpy_orig+0xad/0x140

? __pfx__raw_spin_lock_bh+0x10/0x10

xfrm_update_ae_params+0xe7/0x260

xfrm_new_ae+0x298/0x4e0

? __pfx_xfrm_new_ae+0x10/0x10

? __pfx_xfrm_new_ae+0x10/0x10

xfrm_user_rcv_msg+0x25a/0x410

? __pfx_xfrm_user_rcv_msg+0x10/0x10

? __alloc_skb+0xcf/0x210

? stack_trace_save+0x90/0xd0

? filter_irq_stacks+0x1c/0x70

? __stack_depot_save+0x39/0x4e0

? __kasan_slab_free+0x10a/0x190

? kmem_cache_free+0x9c/0x340

? netlink_recvmsg+0x23c/0x660

? sock_recvmsg+0xeb/0xf0

? __sys_recvfrom+0x13c/0x1f0

? __x64_sys_recvfrom+0x71/0x90

? do_syscall_64+0x3f/0x90

? entry_SYSCALL_64_after_hwframe+0x72/0xdc

? copyout+0x3e/0x50

netlink_rcv_skb+0xd6/0x210

? __pfx_xfrm_user_rcv_msg+0x10/0x10

? __pfx_netlink_rcv_skb+0x10/0x10

? __pfx_sock_has_perm+0x10/0x10

? mutex_lock+0x8d/0xe0

? __pfx_mutex_lock+0x10/0x10

xfrm_netlink_rcv+0x44/0x50

netlink_unicast+0x36f/0x4c0

? __pfx_netlink_unicast+0x10/0x10

? netlink_recvmsg+0x500/0x660

netlink_sendmsg+0x3b7/0x700

This Null-ptr-deref bug is assigned CVE-2023-3772. And this commit

adds additional NULL check in xfrm_update_ae_params to fix the NPD.