From: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
Define (global) data structures to store ids, uids and gids, to which a
SID maps. There are two separate trees, one for SID/uid and another one
for SID/gid.
A new type of key, cifs_idmap_key_type, is used.
Keys are instantiated and searched using credential of the root by
overriding and restoring the credentials of the caller requesting the key.
Once a SID is mapped, it is stored along with the mapped id, in one
of the rb trees and key is released.
Register a pruning function with the shrinker that prunes the rb trees
when memory pressure warrants freeing up cache. Just for now, it is
more like cleaning entire cache than pruning. The subsequent patch has
this function defined.
Signed-off-by: Shirish Pargaonkar <shirishpargaonkar@xxxxxxxxx>
Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
fs/cifs/cifsacl.c | 138 +++++++++++++++++++++++++++++++++++++++++++++++++++
fs/cifs/cifsfs.c | 7 +++
fs/cifs/cifsglob.h | 5 ++
fs/cifs/cifsproto.h | 3 +
4 files changed, 153 insertions(+), 0 deletions(-)
diff --git a/fs/cifs/cifsacl.c b/fs/cifs/cifsacl.c
index 555e8c5..fc1ec64 100644
--- a/fs/cifs/cifsacl.c
+++ b/fs/cifs/cifsacl.c
@@ -23,6 +23,10 @@
#include <linux/fs.h>
#include <linux/slab.h>
+#include <linux/string.h>
+#include <linux/keyctl.h>
+#include <linux/key-type.h>
+#include <keys/user-type.h>
#include "cifspdu.h"
#include "cifsglob.h"
#include "cifsacl.h"
@@ -50,6 +54,140 @@ static const struct cifs_sid sid_authusers = {
/* group users */
static const struct cifs_sid sid_user = {1, 2 , {0, 0, 0, 0, 0, 5}, {} };
+static const struct cred *root_cred;
+
+/*
+ * Run idmap cache shrinker.
+ */
+static int
+cifs_idmap_shrinker(struct shrinker *shrink, int nr_to_scan, gfp_t gfp_mask)
+{
+ /* Use a pruning scheme in a subsequent patch instead */
+ cifs_destroy_idmaptrees();
+ return 0;
+}
+
+static struct shrinker cifs_shrinker = {
+ .shrink = cifs_idmap_shrinker,
+ .seeks = DEFAULT_SEEKS,
+};
+
+static int
+cifs_idmap_key_instantiate(struct key *key, const void *data, size_t datalen)
+{
+ char *payload;
+
+ payload = kmalloc(datalen, GFP_KERNEL);
+ if (!payload)
+ return -ENOMEM;
+
+ memcpy(payload, data, datalen);
+ key->payload.data = payload;
+ return 0;
+}
+
+static inline void
+cifs_idmap_key_destroy(struct key *key)
+{
+ kfree(key->payload.data);
+}
+
+static
+struct key_type cifs_idmap_key_type = {
+ .name = "cifs.cifs_idmap",
+ .instantiate = cifs_idmap_key_instantiate,
+ .destroy = cifs_idmap_key_destroy,
+ .describe = user_describe,
+ .match = user_match,
+};
+
+int
+init_cifs_idmap(void)
+{
+ struct cred *cred;
+ struct key *keyring;
+ int ret;
+
+ cFYI(1, "Registering the %s key type\n", cifs_idmap_key_type.name);
+
+ /* create an override credential set with a special thread keyring in
+ * which requests are cached
+ *
+ * this is used to prevent malicious redirections from being installed
+ * with add_key().
+ */
+ cred = prepare_kernel_cred(NULL);
+ if (!cred)
+ return -ENOMEM;
+
+ keyring = key_alloc(&key_type_keyring, ".cifs_idmap", 0, 0, cred,
+ (KEY_POS_ALL & ~KEY_POS_SETATTR) |
+ KEY_USR_VIEW | KEY_USR_READ,
+ KEY_ALLOC_NOT_IN_QUOTA);
+ if (IS_ERR(keyring)) {
+ ret = PTR_ERR(keyring);
+ goto failed_put_cred;
+ }
+
+ ret = key_instantiate_and_link(keyring, NULL, 0, NULL, NULL);
+ if (ret < 0)
+ goto failed_put_key;
+
+ ret = register_key_type(&cifs_idmap_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 */
+ cred->thread_keyring = keyring;
+ cred->jit_keyring = KEY_REQKEY_DEFL_THREAD_KEYRING;
+ root_cred = cred;
+
+ spin_lock_init(&siduidlock);
+ uidtree = RB_ROOT;
+ spin_lock_init(&sidgidlock);
+ gidtree = RB_ROOT;
+
+ register_shrinker(&cifs_shrinker);
+
+ cFYI(1, "DNS resolver 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_idmap(void)
+{
+ key_revoke(root_cred->thread_keyring);
+ unregister_key_type(&cifs_idmap_key_type);
+ put_cred(root_cred);
+ unregister_shrinker(&cifs_shrinker);
+ cFYI(1, "Unregistered %s key type\n", cifs_idmap_key_type.name);
+}
+
+void
+cifs_destroy_idmaptrees(void)
+{
+ struct rb_root *root;
+ struct rb_node *node;
+
+ root = &uidtree;
+ spin_lock(&siduidlock);
+ while ((node = rb_first(root)))
+ rb_erase(node, root);
+ spin_unlock(&siduidlock);
+
+ root = &gidtree;
+ spin_lock(&sidgidlock);
+ while ((node = rb_first(root)))
+ rb_erase(node, root);
+ spin_unlock(&sidgidlock);
+}
int match_sid(struct cifs_sid *ctsid)
{
diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 120a9cf..805d6ec 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -1043,11 +1043,16 @@ init_cifs(void)
rc = register_key_type(&cifs_spnego_key_type);
if (rc)
goto out_unregister_filesystem;
+ rc = init_cifs_idmap();
+ if (rc)
+ goto out_unregister_keytype;
#endif
return 0;
#ifdef CONFIG_CIFS_UPCALL
+out_unregister_keytype:
+ unregister_key_type(&cifs_spnego_key_type);
out_unregister_filesystem:
unregister_filesystem(&cifs_fs_type);
#endif
@@ -1074,6 +1079,8 @@ exit_cifs(void)
cifs_dfs_release_automount_timer();
#endif
#ifdef CONFIG_CIFS_UPCALL
+ cifs_destroy_idmaptrees();
+ exit_cifs_idmap();
unregister_key_type(&cifs_spnego_key_type);
#endif
unregister_filesystem(&cifs_fs_type);
diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
index 793a55a..4376e74 100644
--- a/fs/cifs/cifsglob.h
+++ b/fs/cifs/cifsglob.h
@@ -861,6 +861,11 @@ GLOBAL_EXTERN bool sign_zero_copy; /* don't copy written pages with signing */
/* reconnect after this many failed echo attempts */
GLOBAL_EXTERN unsigned short echo_retries;
+GLOBAL_EXTERN struct rb_root uidtree;
+GLOBAL_EXTERN struct rb_root gidtree;
+GLOBAL_EXTERN spinlock_t siduidlock;
+GLOBAL_EXTERN spinlock_t sidgidlock;
+
void cifs_oplock_break(struct work_struct *work);
void cifs_oplock_break_get(struct cifsFileInfo *cfile);
void cifs_oplock_break_put(struct cifsFileInfo *cfile);
diff --git a/fs/cifs/cifsproto.h b/fs/cifs/cifsproto.h
index 03b9344..a3d036a 100644
--- a/fs/cifs/cifsproto.h
+++ b/fs/cifs/cifsproto.h
@@ -53,6 +53,9 @@ do { \
cFYI(1, "CIFS VFS: leaving %s (xid = %d) rc = %d", \
__func__, curr_xid, (int)rc); \
} while (0)
+extern int init_cifs_idmap(void);
+extern void exit_cifs_idmap(void);
+extern void cifs_destroy_idmaptrees(void);
extern char *build_path_from_dentry(struct dentry *);
extern char *cifs_build_path_to_root(struct cifs_sb_info *cifs_sb,
struct cifs_tcon *tcon);
--
1.6.0.2
--
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