CVE-2025-38488: 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 cryptmessage when using async crypto

The CVE-2024-50047 fix removed asynchronous crypto handling from cryptmessage(), assuming all crypto operations are synchronous. However, when hardware crypto accelerators are used, this can cause use-after-free crashes:

cryptmessage() // Allocate the creq buffer containing the req creq = smb2getaeadreq(..., &req);

// Async encryption returns -EINPROGRESS immediately rc = enc ? cryptoaeadencrypt(req) : cryptoaeaddecrypt(req);

// Free creq while async operation is still in progress kvfreesensitive(creq, ...);

Hardware crypto modules often implement async AEAD operations for performance. When cryptoaeadencrypt/decrypt() returns -EINPROGRESS, the operation completes asynchronously. Without cryptowaitreq(), 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 cryptoallocaead() with mask=0 doesn't guarantee synchronous operation. Even without CRYPTOALGASYNC in the mask, async implementations can be selected.

Fix by restoring the async crypto handling: - DECLARECRYPTOWAIT(wait) for completion tracking - aeadrequestsetcallback() for async completion notification - cryptowaitreq() 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.