Amazon Linux AMI: CVE-2023-52885: Security patch for kernel (ALAS-2023-1827)

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

SUNRPC: Fix UAF in svc_tcp_listen_data_ready()

After the listener svc_sock is freed, and before invoking svc_tcp_accept()

for the established child sock, there is a window that the newsock

retaining a freed listener svc_sock in sk_user_data which cloning from

parent. In the race window, if data is received on the newsock, we will

observe use-after-free report in svc_tcp_listen_data_ready().

Reproduce by two tasks:

1. while :; do rpc.nfsd 0 ; rpc.nfsd; done

2. while :; do echo "" | ncat -4 127.0.0.1 2049 ; done

KASAN report:

==================================================================

BUG: KASAN: slab-use-after-free in svc_tcp_listen_data_ready+0x1cf/0x1f0 [sunrpc]

Read of size 8 at addr ffff888139d96228 by task nc/102553

CPU: 7 PID: 102553 Comm: nc Not tainted 6.3.0+ #18

Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 11/12/2020

Call Trace:

dump_stack_lvl+0x33/0x50

print_address_description.constprop.0+0x27/0x310

print_report+0x3e/0x70

kasan_report+0xae/0xe0

svc_tcp_listen_data_ready+0x1cf/0x1f0 [sunrpc]

tcp_data_queue+0x9f4/0x20e0

tcp_rcv_established+0x666/0x1f60

tcp_v4_do_rcv+0x51c/0x850

tcp_v4_rcv+0x23fc/0x2e80

ip_protocol_deliver_rcu+0x62/0x300

ip_local_deliver_finish+0x267/0x350

ip_local_deliver+0x18b/0x2d0

ip_rcv+0x2fb/0x370

__netif_receive_skb_one_core+0x166/0x1b0

process_backlog+0x24c/0x5e0

__napi_poll+0xa2/0x500

net_rx_action+0x854/0xc90

__do_softirq+0x1bb/0x5de

do_softirq+0xcb/0x100

...

Allocated by task 102371:

kasan_save_stack+0x1e/0x40

kasan_set_track+0x21/0x30

__kasan_kmalloc+0x7b/0x90

svc_setup_socket+0x52/0x4f0 [sunrpc]

svc_addsock+0x20d/0x400 [sunrpc]

__write_ports_addfd+0x209/0x390 [nfsd]

write_ports+0x239/0x2c0 [nfsd]

nfsctl_transaction_write+0xac/0x110 [nfsd]

vfs_write+0x1c3/0xae0

ksys_write+0xed/0x1c0

do_syscall_64+0x38/0x90

entry_SYSCALL_64_after_hwframe+0x72/0xdc

Freed by task 102551:

kasan_save_stack+0x1e/0x40

kasan_set_track+0x21/0x30

kasan_save_free_info+0x2a/0x50

__kasan_slab_free+0x106/0x190

__kmem_cache_free+0x133/0x270

svc_xprt_free+0x1e2/0x350 [sunrpc]

svc_xprt_destroy_all+0x25a/0x440 [sunrpc]

nfsd_put+0x125/0x240 [nfsd]

nfsd_svc+0x2cb/0x3c0 [nfsd]

write_threads+0x1ac/0x2a0 [nfsd]

nfsctl_transaction_write+0xac/0x110 [nfsd]

vfs_write+0x1c3/0xae0

ksys_write+0xed/0x1c0

do_syscall_64+0x38/0x90

entry_SYSCALL_64_after_hwframe+0x72/0xdc

Fix the UAF by simply doing nothing in svc_tcp_listen_data_ready()

if state != TCP_LISTEN, that will avoid dereferencing svsk for all

child socket.