cifs: fix crash due to race in hmac(md5) handling (bd975d1e) · Commits · 戴 / test

The secmech hmac(md5) structures are present in the TCP_Server_Info struct and can be shared among multiple CIFS sessions. However, the server mutex is not currently held when these structures are allocated and used, which can lead to a kernel crashes, as in the scenario below: mount.cifs(8) #1 mount.cifs(8) #2 Is secmech.sdeschmaccmd5 allocated? // false Is secmech.sdeschmaccmd5 allocated? // false secmech.hmacmd = crypto_alloc_shash.. secmech.sdeschmaccmd5 = kzalloc.. sdeschmaccmd5->shash.tfm = &secmec.hmacmd; secmech.sdeschmaccmd5 = kzalloc // sdeschmaccmd5->shash.tfm // not yet assigned crypto_shash_update() deref NULL sdeschmaccmd5->shash.tfm Unable to handle kernel paging request at virtual address 00000030 epc : 8027ba34 crypto_shash_update+0x38/0x158 ra : 8020f2e8 setup_ntlmv2_rsp+0x4bc/0xa84 Call Trace: crypto_shash_update+0x38/0x158 setup_ntlmv2_rsp+0x4bc/0xa84 build_ntlmssp_auth_blob+0xbc/0x34c sess_auth_rawntlmssp_authenticate+0xac/0x248 CIFS_SessSetup+0xf0/0x178 cifs_setup_session+0x4c/0x84 cifs_get_smb_ses+0x2c8/0x314 cifs_mount+0x38c/0x76c cifs_do_mount+0x98/0x440 mount_fs+0x20/0xc0 vfs_kern_mount+0x58/0x138 do_mount+0x1e8/0xccc SyS_mount+0x88/0xd4 syscall_common+0x30/0x54 Fix this by locking the srv_mutex around the code which uses these hmac(md5) structures. All the other secmech algos already have similar locking. Fixes: ("Limit allocation of crypto mechanisms to dialect which requires") Signed-off-by:

Rabin Vincent <rabinv@axis.com> Acked-by:

Sachin Prabhu <sprabhu@redhat.com> CC: Stable <stable@vger.kernel.org> Signed-off-by:

Steve French <smfrench@gmail.com>

fs/cifs/cifsencrypt.c

+10 −6

Original line number	Diff line number	Diff line
		@@ -743,24 +743,26 @@ setup_ntlmv2_rsp(struct cifs_ses ses, const struct nls_table nls_cp)

		memcpy(ses->auth_key.response + baselen, tiblob, tilen);

		mutex_lock(&ses->server->srv_mutex);

		rc = crypto_hmacmd5_alloc(ses->server);
		if (rc) {
		cifs_dbg(VFS, "could not crypto alloc hmacmd5 rc %d\n", rc);
		goto setup_ntlmv2_rsp_ret;
		goto unlock;
		}

		/* calculate ntlmv2_hash */
		rc = calc_ntlmv2_hash(ses, ntlmv2_hash, nls_cp);
		if (rc) {
		cifs_dbg(VFS, "could not get v2 hash rc %d\n", rc);
		goto setup_ntlmv2_rsp_ret;
		goto unlock;
		}

		/* calculate first part of the client response (CR1) */
		rc = CalcNTLMv2_response(ses, ntlmv2_hash);
		if (rc) {
		cifs_dbg(VFS, "Could not calculate CR1 rc: %d\n", rc);
		goto setup_ntlmv2_rsp_ret;
		goto unlock;
		}

		/* now calculate the session key for NTLMv2 */
		@@ -769,13 +771,13 @@ setup_ntlmv2_rsp(struct cifs_ses ses, const struct nls_table nls_cp)
		if (rc) {
		cifs_dbg(VFS, "%s: Could not set NTLMV2 Hash as a key\n",
		__func__);
		goto setup_ntlmv2_rsp_ret;
		goto unlock;
		}

		rc = crypto_shash_init(&ses->server->secmech.sdeschmacmd5->shash);
		if (rc) {
		cifs_dbg(VFS, "%s: Could not init hmacmd5\n", __func__);
		goto setup_ntlmv2_rsp_ret;
		goto unlock;
		}

		rc = crypto_shash_update(&ses->server->secmech.sdeschmacmd5->shash,
		@@ -783,7 +785,7 @@ setup_ntlmv2_rsp(struct cifs_ses ses, const struct nls_table nls_cp)
		CIFS_HMAC_MD5_HASH_SIZE);
		if (rc) {
		cifs_dbg(VFS, "%s: Could not update with response\n", __func__);
		goto setup_ntlmv2_rsp_ret;
		goto unlock;
		}

		rc = crypto_shash_final(&ses->server->secmech.sdeschmacmd5->shash,
		@@ -791,6 +793,8 @@ setup_ntlmv2_rsp(struct cifs_ses ses, const struct nls_table nls_cp)
		if (rc)
		cifs_dbg(VFS, "%s: Could not generate md5 hash\n", __func__);

		unlock:
		mutex_unlock(&ses->server->srv_mutex);
		setup_ntlmv2_rsp_ret:
		kfree(tiblob);

Admin message