blob: 9edd726275fa88c4b3f33cd1ac208a1b148b6e04 [file] [log] [blame]
From: Rabin Vincent <rabinv@axis.com>
Date: Tue, 19 Jul 2016 09:26:21 +0200
Subject: cifs: fix crash due to race in hmac(md5) handling
commit bd975d1eead2558b76e1079e861eacf1f678b73b upstream.
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>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
fs/cifs/cifsencrypt.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -727,24 +727,26 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, c
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 */
@@ -753,13 +755,13 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, c
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,
@@ -767,7 +769,7 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, c
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,
@@ -775,6 +777,8 @@ setup_ntlmv2_rsp(struct cifs_ses *ses, c
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);