Merge: CVE-2025-37750: smb: client: fix UAF in decryption with multichannel

MR: https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/6935

JIRA: https://issues.redhat.com/browse/RHEL-94457
CVE: CVE-2025-37750

```
commit 9502dd5
Author: Paulo Alcantara <pc@manguebit.com>
Date:   Wed Apr 9 11:14:21 2025 -0300

    smb: client: fix UAF in decryption with multichannel

    After commit f7025d8 ("smb: client: allocate crypto only for
    primary server") and commit b0abcd6 ("smb: client: fix UAF in
    async decryption"), the channels started reusing AEAD TFM from primary
    channel to perform synchronous decryption, but that can't done as
    there could be multiple cifsd threads (one per channel) simultaneously
    accessing it to perform decryption.

    This fixes the following KASAN splat when running fstest generic/249
    with 'vers=3.1.1,multichannel,max_channels=4,seal' against Windows
    Server 2022:

    BUG: KASAN: slab-use-after-free in gf128mul_4k_lle+0xba/0x110
    Read of size 8 at addr ffff8881046c18a0 by task cifsd/986
    CPU: 3 UID: 0 PID: 986 Comm: cifsd Not tainted 6.15.0-rc1 #1
    PREEMPT(voluntary)
    Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-3.fc41
    04/01/2014
    Call Trace:
     <TASK>
     dump_stack_lvl+0x5d/0x80
     print_report+0x156/0x528
     ? gf128mul_4k_lle+0xba/0x110
     ? __virt_addr_valid+0x145/0x300
     ? __phys_addr+0x46/0x90
     ? gf128mul_4k_lle+0xba/0x110
     kasan_report+0xdf/0x1a0
     ? gf128mul_4k_lle+0xba/0x110
     gf128mul_4k_lle+0xba/0x110
     ghash_update+0x189/0x210
     shash_ahash_update+0x295/0x370
     ? __pfx_shash_ahash_update+0x10/0x10
     ? __pfx_shash_ahash_update+0x10/0x10
     ? __pfx_extract_iter_to_sg+0x10/0x10
     ? ___kmalloc_large_node+0x10e/0x180
     ? __asan_memset+0x23/0x50
     crypto_ahash_update+0x3c/0xc0
     gcm_hash_assoc_remain_continue+0x93/0xc0
     crypt_message+0xe09/0xec0 [cifs]
     ? __pfx_crypt_message+0x10/0x10 [cifs]
     ? _raw_spin_unlock+0x23/0x40
     ? __pfx_cifs_readv_from_socket+0x10/0x10 [cifs]
     decrypt_raw_data+0x229/0x380 [cifs]
     ? __pfx_decrypt_raw_data+0x10/0x10 [cifs]
     ? __pfx_cifs_read_iter_from_socket+0x10/0x10 [cifs]
     smb3_receive_transform+0x837/0xc80 [cifs]
     ? __pfx_smb3_receive_transform+0x10/0x10 [cifs]
     ? __pfx___might_resched+0x10/0x10
     ? __pfx_smb3_is_transform_hdr+0x10/0x10 [cifs]
     cifs_demultiplex_thread+0x692/0x1570 [cifs]
     ? __pfx_cifs_demultiplex_thread+0x10/0x10 [cifs]
     ? rcu_is_watching+0x20/0x50
     ? rcu_lockdep_current_cpu_online+0x62/0xb0
     ? find_held_lock+0x32/0x90
     ? kvm_sched_clock_read+0x11/0x20
     ? local_clock_noinstr+0xd/0xd0
     ? trace_irq_enable.constprop.0+0xa8/0xe0
     ? __pfx_cifs_demultiplex_thread+0x10/0x10 [cifs]
     kthread+0x1fe/0x380
     ? kthread+0x10f/0x380
     ? __pfx_kthread+0x10/0x10
     ? local_clock_noinstr+0xd/0xd0
     ? ret_from_fork+0x1b/0x60
     ? local_clock+0x15/0x30
     ? lock_release+0x29b/0x390
     ? rcu_is_watching+0x20/0x50
     ? __pfx_kthread+0x10/0x10
     ret_from_fork+0x31/0x60
     ? __pfx_kthread+0x10/0x10
     ret_from_fork_asm+0x1a/0x30
     </TASK>

    Tested-by: David Howells <dhowells@redhat.com>
    Reported-by: Steve French <stfrench@microsoft.com>
    Closes: https://lore.kernel.org/r/CAH2r5mu6Yc0-RJXM3kFyBYUB09XmXBrNodOiCVR4EDrmxq5Szg@mail.gmail.com
    Fixes: f7025d8 ("smb: client: allocate crypto only for primary server")
    Fixes: b0abcd6 ("smb: client: fix UAF in async decryption")
    Signed-off-by: Paulo Alcantara (Red Hat) <pc@manguebit.com>
    Signed-off-by: Steve French <stfrench@microsoft.com>
```

Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>

---

<small>Created 2025-05-29 21:09 UTC by backporter - [KWF FAQ](https://red.ht/kernel_workflow_doc) - [Slack #team-kernel-workflow](https://redhat-internal.slack.com/archives/C04LRUPMJQ5) - [Source](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/webhook/utils/backporter.py) - [Documentation](https://gitlab.com/cki-project/kernel-workflow/-/blob/main/docs/README.backporter.md) - [Report an issue](https://issues.redhat.com/secure/CreateIssueDetails!init.jspa?pid=12334433&issuetype=1&priority=4&summary=backporter+webhook+issue&components=kernel-workflow+/+backporter)</small>

Approved-by: Jay Shin <jaeshin@redhat.com>
Approved-by: Scott Mayhew <smayhew@redhat.com>
Approved-by: Benjamin Coddington <bcodding@redhat.com>
Approved-by: David Howells <dhowells@redhat.com>
Approved-by: CKI KWF Bot <cki-ci-bot+kwf-gitlab-com@redhat.com>

Merged-by: Augusto Caringi <acaringi@redhat.com>

Author: caringi

fs/smb/client/cifsencrypt.c

@@ -690,18 +690,12 @@ cifs_crypto_secmech_release(struct TCP_Server_Info *server)
 	cifs_free_hash(&server->secmech.md5);
 	cifs_free_hash(&server->secmech.sha512);
 
-	if (!SERVER_IS_CHAN(server)) {
-		if (server->secmech.enc) {
-			crypto_free_aead(server->secmech.enc);
-			server->secmech.enc = NULL;
-		}
-
-		if (server->secmech.dec) {
-			crypto_free_aead(server->secmech.dec);
-			server->secmech.dec = NULL;
-		}
-	} else {
+	if (server->secmech.enc) {
+		crypto_free_aead(server->secmech.enc);
 		server->secmech.enc = NULL;
+	}
+	if (server->secmech.dec) {
+		crypto_free_aead(server->secmech.dec);
 		server->secmech.dec = NULL;
 	}
 }

fs/smb/client/smb2ops.c

@@ -4448,9 +4448,9 @@ decrypt_raw_data(struct TCP_Server_Info *server, char *buf,
 			return rc;
 		}
 	} else {
-		if (unlikely(!server->secmech.dec))
-			return -EIO;
-
+		rc = smb3_crypto_aead_allocate(server);
+		if (unlikely(rc))
+			return rc;
 		tfm = server->secmech.dec;
 	}
 

fs/smb/client/smb2pdu.c

@@ -1249,15 +1249,8 @@ SMB2_negotiate(const unsigned int xid,
 			cifs_server_dbg(VFS, "Missing expected negotiate contexts\n");
 	}
 
-	if (server->cipher_type && !rc) {
-		if (!SERVER_IS_CHAN(server)) {
-			rc = smb3_crypto_aead_allocate(server);
-		} else {
-			/* For channels, just reuse the primary server crypto secmech. */
-			server->secmech.enc = server->primary_server->secmech.enc;
-			server->secmech.dec = server->primary_server->secmech.dec;
-		}
-	}
+	if (server->cipher_type && !rc)
+		rc = smb3_crypto_aead_allocate(server);
 neg_exit:
 	free_rsp_buf(resp_buftype, rsp);
 	return rc;