smb: client: fix UAF in async decryption
CVE: CVE-2024-50047
Component: kernel
CWE: CWE-416
Severity: Moderate
CVSS v3: 7.4/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
Release date: 2024-10-21T00:00:00+00:00

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

smb: client: fix UAF in async decryption

Doing an async decryption (large read) crashes with a
slab-use-after-free way down in the crypto API.

Reproducer:
    # mount.cifs -o ...,seal,esize=1 //srv/share /mnt
    # dd if=/mnt/largefile of=/dev/null
    ...
    [  194.196391] ==================================================================
    [  194.196844] BUG: KASAN: slab-use-after-free in gf128mul_4k_lle+0xc1/0x110
    [  194.197269] Read of size 8 at addr ffff888112bd0448 by task kworker/u77:2/899
    [  194.197707]
    [  194.197818] CPU: 12 UID: 0 PID: 899 Comm: kworker/u77:2 Not tainted 6.11.0-lku-00028-gfca3ca14a17a-dirty #43
    [  194.198400] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS rel-1.16.2-3-gd478f380-prebuilt.qemu.org 04/01/2014
    [  194.199046] Workqueue: smb3decryptd smb2_decrypt_offload [cifs]
    [  194.200032] Call Trace:
    [  194.200191]  <TASK>
    [  194.200327]  dump_stack_lvl+0x4e/0x70
    [  194.200558]  ? gf128mul_4k_lle+0xc1/0x110
    [  194.200809]  print_report+0x174/0x505
    [  194.201040]  ? __pfx__raw_spin_lock_irqsave+0x10/0x10
    [  194.201352]  ? srso_return_thunk+0x5/0x5f
    [  194.201604]  ? __virt_addr_valid+0xdf/0x1c0
    [  194.201868]  ? gf128mul_4k_lle+0xc1/0x110
    [  194.202128]  kasan_report+0xc8/0x150
    [  194.202361]  ? gf128mul_4k_lle+0xc1/0x110
    [  194.202616]  gf128mul_4k_lle+0xc1/0x110
    [  194.202863]  ghash_update+0x184/0x210
    [  194.203103]  shash_ahash_update+0x184/0x2a0
    [  194.203377]  ? __pfx_shash_ahash_update+0x10/0x10
    [  194.203651]  ? srso_return_thunk+0x5/0x5f
    [  194.203877]  ? crypto_gcm_init_common+0x1ba/0x340
    [  194.204142]  gcm_hash_assoc_remain_continue+0x10a/0x140
    [  194.204434]  crypt_message+0xec1/0x10a0 [cifs]
    [  194.206489]  ? __pfx_crypt_message+0x10/0x10 [cifs]
    [  194.208507]  ? srso_return_thunk+0x5/0x5f
    [  194.209205]  ? srso_return_thunk+0x5/0x5f
    [  194.209925]  ? srso_return_thunk+0x5/0x5f
    [  194.210443]  ? srso_return_thunk+0x5/0x5f
    [  194.211037]  decrypt_raw_data+0x15f/0x250 [cifs]
    [  194.212906]  ? __pfx_decrypt_raw_data+0x10/0x10 [cifs]
    [  194.214670]  ? srso_return_thunk+0x5/0x5f
    [  194.215193]  smb2_decrypt_offload+0x12a/0x6c0 [cifs]

This is because TFM is being used in parallel.

Fix this by allocating a new AEAD TFM for async decryption, but keep
the existing one for synchronous READ cases (similar to what is done
in smb3_calc_signature()).

Also remove the calls to aead_request_set_callback() and
crypto_wait_req() since it's always going to be a synchronous operation.

Statement: This issue is considered to be a moderate impact flaw, as the exploitation for this will need an ADMIN (or ROOT) privilege (PR:H).

Remediation:
For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.