From bd975d1eead2558b76e1079e861eacf1f678b73b Mon Sep 17 00:00:00 2001 From: Rabin Vincent Date: Tue, 19 Jul 2016 09:26:21 +0200 Subject: [PATCH] cifs: fix crash due to race in hmac(md5) handling 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: 95dc8dd14e2e84cc ("Limit allocation of crypto mechanisms to dialect which requires") Signed-off-by: Rabin Vincent Acked-by: Sachin Prabhu CC: Stable Signed-off-by: Steve French --- fs/cifs/cifsencrypt.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c index 6aeb8d4616a4..8347c90cf483 100644 --- a/fs/cifs/cifsencrypt.c +++ b/fs/cifs/cifsencrypt.c @@ -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); -- 2.20.1