[PATCH AUTOSEL 6.10 69/70] smb: client: fix UAF in async decryption

Sasha Levin
2024-10-04T18:24:27Z

From: Enzo Matsumiya <ematsumiya@suse.de>

[ Upstream commit b0abcd65ec545701b8793e12bc27dc98042b151a ]

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.

Signed-off-by: Enzo Matsumiya <ematsumiya@suse.de>
Signed-off-by: Steve French <stfrench@microsoft.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/smb/client/smb2ops.c | 47 ++++++++++++++++++++++++-----------------
fs/smb/client/smb2pdu.c | 6 ++++++
2 files changed, 34 insertions(+), 19 deletions(-)

diff --git a/fs/smb/client/smb2ops.c b/fs/smb/client/smb2ops.c
index 1d6e8eacdd742..a8ebf3333c6cc 100644
--- a/fs/smb/client/smb2ops.c
+++ b/fs/smb/client/smb2ops.c
@@ -4287,7 +4287,7 @@ smb2_get_enc_key(struct TCP_Server_Info *server, __u64 ses_id, int enc, u8 *key)
*/
static int
crypt_message(struct TCP_Server_Info *server, int num_rqst,
- struct smb_rqst *rqst, int enc)
+ struct smb_rqst *rqst, int enc, struct crypto_aead *tfm)
{
struct smb2_transform_hdr *tr_hdr =
(struct smb2_transform_hdr *)rqst[0].rq_iov[0].iov_base;
@@ -4298,8 +4298,6 @@ crypt_message(struct TCP_Server_Info *server, int num_rqst,
u8 key[SMB3_ENC_DEC_KEY_SIZE];
struct aead_request *req;
u8 *iv;
- DECLARE_CRYPTO_WAIT(wait);
- struct crypto_aead *tfm;
unsigned int crypt_len = le32_to_cpu(tr_hdr->OriginalMessageSize);
void *creq;
size_t sensitive_size;
@@ -4311,14 +4309,6 @@ crypt_message(struct TCP_Server_Info *server, int num_rqst,
return rc;
}

- rc = smb3_crypto_aead_allocate(server);
- if (rc) {
- cifs_server_dbg(VFS, "%s: crypto alloc failed\n", __func__);
- return rc;
- }
-
- tfm = enc ? server->secmech.enc : server->secmech.dec;
-
if ((server->cipher_type == SMB2_ENCRYPTION_AES256_CCM) ||
(server->cipher_type == SMB2_ENCRYPTION_AES256_GCM))
rc = crypto_aead_setkey(tfm, key, SMB3_GCM256_CRYPTKEY_SIZE);
@@ -4358,11 +4348,7 @@ crypt_message(struct TCP_Server_Info *server, int num_rqst,
aead_request_set_crypt(req, sg, sg, crypt_len, iv);
aead_request_set_ad(req, assoc_data_len);

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

if (!rc && enc)
memcpy(&tr_hdr->Signature, sign, SMB2_SIGNATURE_SIZE);
@@ -4468,7 +4454,7 @@ smb3_init_transform_rq(struct TCP_Server_Info *server, int num_rqst,
/* fill the 1st iov with a transform header */
fill_transform_hdr(tr_hdr, orig_len, old_rq, server->cipher_type);

- rc = crypt_message(server, num_rqst, new_rq, 1);
+ rc = crypt_message(server, num_rqst, new_rq, 1, server->secmech.enc);
cifs_dbg(FYI, "Encrypt message returned %d\n", rc);
if (rc)
goto err_free;
@@ -4493,8 +4479,9 @@ decrypt_raw_data(struct TCP_Server_Info *server, char *buf,
unsigned int buf_data_size, struct iov_iter *iter,
bool is_offloaded)
{
- struct kvec iov[2];
+ struct crypto_aead *tfm;
struct smb_rqst rqst = {NULL};
+ struct kvec iov[2];
size_t iter_size = 0;
int rc;

@@ -4510,9 +4497,31 @@ decrypt_raw_data(struct TCP_Server_Info *server, char *buf,
iter_size = iov_iter_count(iter);
}

- rc = crypt_message(server, 1, &rqst, 0);
+ if (is_offloaded) {
+ if ((server->cipher_type == SMB2_ENCRYPTION_AES128_GCM) ||
+ (server->cipher_type == SMB2_ENCRYPTION_AES256_GCM))
+ tfm = crypto_alloc_aead("gcm(aes)", 0, 0);
+ else
+ tfm = crypto_alloc_aead("ccm(aes)", 0, 0);
+ if (IS_ERR(tfm)) {
+ rc = PTR_ERR(tfm);
+ cifs_server_dbg(VFS, "%s: Failed alloc decrypt TFM, rc=%d\n", __func__, rc);
+
+ return rc;
+ }
+ } else {
+ if (unlikely(!server->secmech.dec))
+ return -EIO;
+
+ tfm = server->secmech.dec;
+ }
+
+ rc = crypt_message(server, 1, &rqst, 0, tfm);
cifs_dbg(FYI, "Decrypt message returned %d\n", rc);

+ if (is_offloaded)
+ crypto_free_aead(tfm);
+
if (rc)
return rc;

diff --git a/fs/smb/client/smb2pdu.c b/fs/smb/client/smb2pdu.c
index 8e02e9f45e0e1..3a4ac6694161e 100644
--- a/fs/smb/client/smb2pdu.c
+++ b/fs/smb/client/smb2pdu.c
@@ -1265,6 +1265,12 @@ SMB2_negotiate(const unsigned int xid,
else
cifs_server_dbg(VFS, "Missing expected negotiate contexts\n");
}
+
+ if (server->cipher_type && !rc) {
+ rc = smb3_crypto_aead_allocate(server);
+ if (rc)
+ cifs_server_dbg(VFS, "%s: crypto alloc failed, rc=%d\n", __func__, rc);
+ }
neg_exit:
free_rsp_buf(resp_buftype, rsp);
return rc;
--
2.43.0