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.
Fixes: b0abcd65ec54 ("smb: client: fix UAF in async decryption")
Link: https://lore.kernel.org/all/8b784a13-87b0-4131-9ff9-7a8993538749@huaweicloud.com/
Cc: stable@vger.kernel.org
Reviewed-by: Paulo Alcantara (Red Hat) <pc@manguebit.org>
Signed-off-by: Wang Zhaolong <wangzhaolong@huaweicloud.com>
Signed-off-by: Steve French <stfrench@microsoft.com>
u8 key[SMB3_ENC_DEC_KEY_SIZE];
struct aead_request *req;
u8 *iv;
+ DECLARE_CRYPTO_WAIT(wait);
unsigned int crypt_len = le32_to_cpu(tr_hdr->OriginalMessageSize);
void *creq;
size_t sensitive_size;
aead_request_set_crypt(req, sg, sg, crypt_len, iv);
aead_request_set_ad(req, assoc_data_len);
- rc = enc ? crypto_aead_encrypt(req) : crypto_aead_decrypt(req);
+ aead_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG,
+ crypto_req_done, &wait);
+
+ rc = crypto_wait_req(enc ? crypto_aead_encrypt(req)
+ : crypto_aead_decrypt(req), &wait);
if (!rc && enc)
memcpy(&tr_hdr->Signature, sign, SMB2_SIGNATURE_SIZE);