🛡️ CVE-2025-38488 — debian-linux

smb: client: fix use-after-free in crypt_message when using async crypto

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

smb: client: fix use-after-free in crypt_message when using async crypto

The CVE-2024-50047 fix removed asynchronous crypto handling from

crypt_message(), assuming all crypto operations are synchronous.

However, when hardware crypto accelerators are used, this can cause

use-after-free crashes:

crypt_message()

// Allocate the creq buffer containing the req

creq = smb2_get_aead_req(..., &req);

// Async encryption returns -EINPROGRESS immediately

rc = enc ? crypto_aead_encrypt(req) : crypto_aead_decrypt(req);

// Free creq while async operation is still in progress

kvfree_sensitive(creq, ...);

Hardware crypto modules often implement async AEAD operations for

performance. When crypto_aead_encrypt/decrypt() returns -EINPROGRESS,

the operation completes asynchronously. Without crypto_wait_req(),

the function immediately frees the request buffer, leading to crashes

when the driver later accesses the freed memory.

This results in a use-after-free condition when the hardware crypto

driver later accesses the freed request structure, leading to kernel

crashes with NULL pointer dereferences.

The issue occurs because crypto_alloc_aead() with mask=0 doesn't

guarantee synchronous operation. Even without CRYPTO_ALG_ASYNC in

the mask, async implementations can be selected.

Fix by restoring the async crypto handling:

• DECLARE_CRYPTO_WAIT(wait) for completion tracking
• aead_request_set_callback() for async completion notification
• crypto_wait_req() to wait for operation completion

This ensures the request buffer isn't freed until the crypto operation

completes, whether synchronous or asynchronous, while preserving the

CVE-2024-50047 fix.