CIFS: Fix BUG() in calc_seckey()

Andy Lutromirski's new virtually mapped kernel stack allocations moves
kernel stacks the vmalloc area. This triggers the bug
 kernel BUG at ./include/linux/scatterlist.h:140!
at calc_seckey()->sg_init()

Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Reviewed-by: Jeff Layton <jlayton@redhat.com>

1 files changed, 8 insertions, 3 deletions

diff --git a/fs/cifs/cifsencrypt.c b/fs/cifs/cifsencrypt.c
index 8347c90cf483..5eb04129f938 100644
--- a/fs/cifs/cifsencrypt.c
+++ b/fs/cifs/cifsencrypt.c
@@ -808,7 +808,11 @@ calc_seckey(struct cifs_ses *ses)
         struct crypto_skcipher *tfm_arc4;
         struct scatterlist sgin, sgout;
         struct skcipher_request *req;
-        unsigned char sec_key[CIFS_SESS_KEY_SIZE]; /* a nonce */
+        unsigned char *sec_key;
+
+        sec_key = kmalloc(CIFS_SESS_KEY_SIZE, GFP_KERNEL);
+        if (sec_key == NULL)
+                return -ENOMEM;
 
         get_random_bytes(sec_key, CIFS_SESS_KEY_SIZE);
 
@@ -816,7 +820,7 @@ calc_seckey(struct cifs_ses *ses)
         if (IS_ERR(tfm_arc4)) {
                 rc = PTR_ERR(tfm_arc4);
                 cifs_dbg(VFS, "could not allocate crypto API arc4\n");
-                return rc;
+                goto out;
         }
 
         rc = crypto_skcipher_setkey(tfm_arc4, ses->auth_key.response,
@@ -854,7 +858,8 @@ calc_seckey(struct cifs_ses *ses)
 
 out_free_cipher:
         crypto_free_skcipher(tfm_arc4);
-
+out:
+        kfree(sec_key);
         return rc;
 }