Patch "cifs: Create dedicated keyring for spnego operations" has been added to the 4.6-stable tree

gregkh
2016-05-29T21:52:22Z

This is a note to let you know that I've just added the patch titled

cifs: Create dedicated keyring for spnego operations

to the 4.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
cifs-create-dedicated-keyring-for-spnego-operations.patch
and it can be found in the queue-4.6 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.

>From b74cb9a80268be5c80cf4c87c74debf0ff2129ac Mon Sep 17 00:00:00 2001
From: Sachin Prabhu <sprabhu@redhat.com>
Date: Tue, 17 May 2016 18:20:13 -0500
Subject: cifs: Create dedicated keyring for spnego operations

From: Sachin Prabhu <sprabhu@redhat.com>

commit b74cb9a80268be5c80cf4c87c74debf0ff2129ac upstream.

The session key is the default keyring set for request_key operations.
This session key is revoked when the user owning the session logs out.
Any long running daemon processes started by this session ends up with
revoked session keyring which prevents these processes from using the
request_key mechanism from obtaining the krb5 keys.

The problem has been reported by a large number of autofs users. The
problem is also seen with multiuser mounts where the share may be used
by processes run by a user who has since logged out. A reproducer using
automount is available on the Red Hat bz.

The patch creates a new keyring which is used to cache cifs spnego
upcalls.

Red Hat bz: 1267754

Signed-off-by: Sachin Prabhu <sprabhu@redhat.com>
Reported-by: Scott Mayhew <smayhew@redhat.com>
Reviewed-by: Shirish Pargaonkar <shirishpargaonkar@gmail.com>
Signed-off-by: Steve French <smfrench@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
fs/cifs/cifs_spnego.c | 67 ++++++++++++++++++++++++++++++++++++++++++++++++++
fs/cifs/cifsfs.c | 4 +-
fs/cifs/cifsproto.h | 2 +
3 files changed, 71 insertions(+), 2 deletions(-)

--- a/fs/cifs/cifs_spnego.c
+++ b/fs/cifs/cifs_spnego.c
@@ -24,10 +24,13 @@
#include <linux/string.h>
#include <keys/user-type.h>
#include <linux/key-type.h>
+#include <linux/keyctl.h>
#include <linux/inet.h>
#include "cifsglob.h"
#include "cifs_spnego.h"
#include "cifs_debug.h"
+#include "cifsproto.h"
+static const struct cred *spnego_cred;

/* create a new cifs key */
static int
@@ -102,6 +105,7 @@ cifs_get_spnego_key(struct cifs_ses *ses
size_t desc_len;
struct key *spnego_key;
const char *hostname = server->hostname;
+ const struct cred *saved_cred;

/* length of fields (with semicolons): ver=0xyz ip4=ipaddress
host=hostname sec=mechanism uid=0xFF user=username */
@@ -163,7 +167,9 @@ cifs_get_spnego_key(struct cifs_ses *ses
sprintf(dp, ";pid=0x%x", current->pid);

cifs_dbg(FYI, "key description = %s\n", description);
+ saved_cred = override_creds(spnego_cred);
spnego_key = request_key(&cifs_spnego_key_type, description, "");
+ revert_creds(saved_cred);

#ifdef CONFIG_CIFS_DEBUG2
if (cifsFYI && !IS_ERR(spnego_key)) {
@@ -177,3 +183,64 @@ out:
kfree(description);
return spnego_key;
}
+
+int
+init_cifs_spnego(void)
+{
+ struct cred *cred;
+ struct key *keyring;
+ int ret;
+
+ cifs_dbg(FYI, "Registering the %s key type\n",
+ cifs_spnego_key_type.name);
+
+ /*
+ * Create an override credential set with special thread keyring for
+ * spnego upcalls.
+ */
+
+ cred = prepare_kernel_cred(NULL);
+ if (!cred)
+ return -ENOMEM;
+
+ keyring = keyring_alloc(".cifs_spnego",
+ GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
+ (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+ KEY_USR_VIEW | KEY_USR_READ,
+ KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
+ if (IS_ERR(keyring)) {
+ ret = PTR_ERR(keyring);
+ goto failed_put_cred;
+ }
+
+ ret = register_key_type(&cifs_spnego_key_type);
+ if (ret < 0)
+ goto failed_put_key;
+
+ /*
+ * instruct request_key() to use this special keyring as a cache for
+ * the results it looks up
+ */
+ set_bit(KEY_FLAG_ROOT_CAN_CLEAR, &keyring->flags);
+ cred->thread_keyring = keyring;
+ cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
+ spnego_cred = cred;
+
+ cifs_dbg(FYI, "cifs spnego keyring: %d\n", key_serial(keyring));
+ return 0;
+
+failed_put_key:
+ key_put(keyring);
+failed_put_cred:
+ put_cred(cred);
+ return ret;
+}
+
+void
+exit_cifs_spnego(void)
+{
+ key_revoke(spnego_cred->thread_keyring);
+ unregister_key_type(&cifs_spnego_key_type);
+ put_cred(spnego_cred);
+ cifs_dbg(FYI, "Unregistered %s key type\n", cifs_spnego_key_type.name);
+}
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1307,7 +1307,7 @@ init_cifs(void)
goto out_destroy_mids;

#ifdef CONFIG_CIFS_UPCALL
- rc = register_key_type(&cifs_spnego_key_type);
+ rc = init_cifs_spnego();
if (rc)
goto out_destroy_request_bufs;
#endif /* CONFIG_CIFS_UPCALL */
@@ -1330,7 +1330,7 @@ out_init_cifs_idmap:
out_register_key_type:
#endif
#ifdef CONFIG_CIFS_UPCALL
- unregister_key_type(&cifs_spnego_key_type);
+ exit_cifs_spnego();
out_destroy_request_bufs:
#endif
cifs_destroy_request_bufs();
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -60,6 +60,8 @@ do { \
} while (0)
extern int init_cifs_idmap(void);
extern void exit_cifs_idmap(void);
+extern int init_cifs_spnego(void);
+extern void exit_cifs_spnego(void);
extern char *build_path_from_dentry(struct dentry *);
extern char *cifs_build_path_to_root(struct smb_vol *vol,
struct cifs_sb_info *cifs_sb,

Patches currently in stable-queue which might be from sprabhu@redhat.com are

queue-4.6/remove-directory-incorrectly-tries-to-set-delete-on-close-on-non-empty-directories.patch
queue-4.6/cifs-create-dedicated-keyring-for-spnego-operations.patch