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authorRabin Vincent <rabinv@axis.com>2016-07-19 09:26:21 +0200
committerSteve French <smfrench@gmail.com>2016-07-20 03:03:27 -0500
commitbd975d1eead2558b76e1079e861eacf1f678b73b (patch)
tree6fe90e6b998b906ecece91e0232009081885ad81 /fs/cifs/cifsencrypt.c
parentb782fcc1cbeb7e336c0ed1f00004b2208f48ffe0 (diff)
downloadlinux-bd975d1eead2558b76e1079e861eacf1f678b73b.tar.bz2
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 <rabinv@axis.com> Acked-by: Sachin Prabhu <sprabhu@redhat.com> CC: Stable <stable@vger.kernel.org> Signed-off-by: Steve French <smfrench@gmail.com>
Diffstat (limited to 'fs/cifs/cifsencrypt.c')
-rw-r--r--fs/cifs/cifsencrypt.c16
1 files 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);