keys: make the keyring quotas controllable through /proc/sys

Make the keyring quotas controllable through /proc/sys files:

 (*) /proc/sys/kernel/keys/root_maxkeys
     /proc/sys/kernel/keys/root_maxbytes

     Maximum number of keys that root may have and the maximum total number of
     bytes of data that root may have stored in those keys.

 (*) /proc/sys/kernel/keys/maxkeys
     /proc/sys/kernel/keys/maxbytes

     Maximum number of keys that each non-root user may have and the maximum
     total number of bytes of data that each of those users may have stored in
     their keys.

Also increase the quotas as a number of people have been complaining that it's
not big enough.  I'm not sure that it's big enough now either, but on the
other hand, it can now be set in /etc/sysctl.conf.

Signed-off-by: David Howells <dhowells@redhat.com>
Cc: <kwc@citi.umich.edu>
Cc: <arunsr@cse.iitk.ac.in>
Cc: <dwalsh@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

6 files changed, 94 insertions, 15 deletions

diff --git a/security/keys/Makefile b/security/keys/Makefile
index 5145adf..747a464 100644
--- a/security/keys/Makefile
+++ b/security/keys/Makefile
@@ -14,3 +14,4 @@ obj-y := \
 
 obj-$(CONFIG_KEYS_COMPAT) += compat.o
 obj-$(CONFIG_PROC_FS) += proc.o
+obj-$(CONFIG_SYSCTL) += sysctl.o
diff --git a/security/keys/internal.h b/security/keys/internal.h
index 2ab3885..8c05587 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -57,10 +57,6 @@ struct key_user {
 	int			qnbytes;	/* number of bytes allocated to this user */
 };
 
-#define KEYQUOTA_MAX_KEYS	100
-#define KEYQUOTA_MAX_BYTES	10000
-#define KEYQUOTA_LINK_BYTES	4		/* a link in a keyring is worth 4 bytes */
-
 extern struct rb_root	key_user_tree;
 extern spinlock_t	key_user_lock;
 extern struct key_user	root_key_user;
@@ -68,6 +64,16 @@ extern struct key_user	root_key_user;
 extern struct key_user *key_user_lookup(uid_t uid);
 extern void key_user_put(struct key_user *user);
 
+/*
+ * key quota limits
+ * - root has its own separate limits to everyone else
+ */
+extern unsigned key_quota_root_maxkeys;
+extern unsigned key_quota_root_maxbytes;
+extern unsigned key_quota_maxkeys;
+extern unsigned key_quota_maxbytes;
+
+#define KEYQUOTA_LINK_BYTES	4		/* a link in a keyring is worth 4 bytes */
 
 
 extern struct rb_root key_serial_tree;
diff --git a/security/keys/key.c b/security/keys/key.c
index 46f125a..14948cf 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -27,6 +27,11 @@ DEFINE_SPINLOCK(key_serial_lock);
 struct rb_root	key_user_tree; /* tree of quota records indexed by UID */
 DEFINE_SPINLOCK(key_user_lock);
 
+unsigned int key_quota_root_maxkeys = 200;	/* root's key count quota */
+unsigned int key_quota_root_maxbytes = 20000;	/* root's key space quota */
+unsigned int key_quota_maxkeys = 200;		/* general key count quota */
+unsigned int key_quota_maxbytes = 20000;	/* general key space quota */
+
 static LIST_HEAD(key_types_list);
 static DECLARE_RWSEM(key_types_sem);
 
@@ -236,11 +241,16 @@ struct key *key_alloc(struct key_type *type, const char *desc,
 	/* check that the user's quota permits allocation of another key and
 	 * its description */
 	if (!(flags & KEY_ALLOC_NOT_IN_QUOTA)) {
+		unsigned maxkeys = (uid == 0) ?
+			key_quota_root_maxkeys : key_quota_maxkeys;
+		unsigned maxbytes = (uid == 0) ?
+			key_quota_root_maxbytes : key_quota_maxbytes;
+
 		spin_lock(&user->lock);
 		if (!(flags & KEY_ALLOC_QUOTA_OVERRUN)) {
-			if (user->qnkeys + 1 >= KEYQUOTA_MAX_KEYS ||
-			    user->qnbytes + quotalen >= KEYQUOTA_MAX_BYTES
-			    )
+			if (user->qnkeys + 1 >= maxkeys ||
+			    user->qnbytes + quotalen >= maxbytes ||
+			    user->qnbytes + quotalen < user->qnbytes)
 				goto no_quota;
 		}
 
@@ -345,11 +355,14 @@ int key_payload_reserve(struct key *key, size_t datalen)
 
 	/* contemplate the quota adjustment */
 	if (delta != 0 && test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
+		unsigned maxbytes = (key->user->uid == 0) ?
+			key_quota_root_maxbytes : key_quota_maxbytes;
+
 		spin_lock(&key->user->lock);
 
 		if (delta > 0 &&
-		    key->user->qnbytes + delta > KEYQUOTA_MAX_BYTES
-		    ) {
+		    (key->user->qnbytes + delta >= maxbytes ||
+		     key->user->qnbytes + delta < key->user->qnbytes)) {
 			ret = -EDQUOT;
 		}
 		else {
diff --git a/security/keys/keyctl.c b/security/keys/keyctl.c
index 993be63..acc9c89 100644
--- a/security/keys/keyctl.c
+++ b/security/keys/keyctl.c
@@ -731,10 +731,16 @@ long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
 
 		/* transfer the quota burden to the new user */
 		if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
+			unsigned maxkeys = (uid == 0) ?
+				key_quota_root_maxkeys : key_quota_maxkeys;
+			unsigned maxbytes = (uid == 0) ?
+				key_quota_root_maxbytes : key_quota_maxbytes;
+
 			spin_lock(&newowner->lock);
-			if (newowner->qnkeys + 1 >= KEYQUOTA_MAX_KEYS ||
-			    newowner->qnbytes + key->quotalen >=
-			    KEYQUOTA_MAX_BYTES)
+			if (newowner->qnkeys + 1 >= maxkeys ||
+			    newowner->qnbytes + key->quotalen >= maxbytes ||
+			    newowner->qnbytes + key->quotalen <
+			    newowner->qnbytes)
 				goto quota_overrun;
 
 			newowner->qnkeys++;
diff --git a/security/keys/proc.c b/security/keys/proc.c
index e54679b..f619170 100644
--- a/security/keys/proc.c
+++ b/security/keys/proc.c
@@ -242,6 +242,10 @@ static int proc_key_users_show(struct seq_file *m, void *v)
 {
 	struct rb_node *_p = v;
 	struct key_user *user = rb_entry(_p, struct key_user, node);
+	unsigned maxkeys = (user->uid == 0) ?
+		key_quota_root_maxkeys : key_quota_maxkeys;
+	unsigned maxbytes = (user->uid == 0) ?
+		key_quota_root_maxbytes : key_quota_maxbytes;
 
 	seq_printf(m, "%5u: %5d %d/%d %d/%d %d/%d\n",
 		   user->uid,
@@ -249,10 +253,9 @@ static int proc_key_users_show(struct seq_file *m, void *v)
 		   atomic_read(&user->nkeys),
 		   atomic_read(&user->nikeys),
 		   user->qnkeys,
-		   KEYQUOTA_MAX_KEYS,
+		   maxkeys,
 		   user->qnbytes,
-		   KEYQUOTA_MAX_BYTES
-		   );
+		   maxbytes);
 
 	return 0;
 
diff --git a/security/keys/sysctl.c b/security/keys/sysctl.c
new file mode 100644
index 0000000..b611d49
--- /dev/null
+++ b/security/keys/sysctl.c
@@ -0,0 +1,50 @@
+/* Key management controls
+ *
+ * Copyright (C) 2008 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/key.h>
+#include <linux/sysctl.h>
+#include "internal.h"
+
+ctl_table key_sysctls[] = {
+	{
+		.ctl_name = CTL_UNNUMBERED,
+		.procname = "maxkeys",
+		.data = &key_quota_maxkeys,
+		.maxlen = sizeof(unsigned),
+		.mode = 0644,
+		.proc_handler = &proc_dointvec,
+	},
+	{
+		.ctl_name = CTL_UNNUMBERED,
+		.procname = "maxbytes",
+		.data = &key_quota_maxbytes,
+		.maxlen = sizeof(unsigned),
+		.mode = 0644,
+		.proc_handler = &proc_dointvec,
+	},
+	{
+		.ctl_name = CTL_UNNUMBERED,
+		.procname = "root_maxkeys",
+		.data = &key_quota_root_maxkeys,
+		.maxlen = sizeof(unsigned),
+		.mode = 0644,
+		.proc_handler = &proc_dointvec,
+	},
+	{
+		.ctl_name = CTL_UNNUMBERED,
+		.procname = "root_maxbytes",
+		.data = &key_quota_root_maxbytes,
+		.maxlen = sizeof(unsigned),
+		.mode = 0644,
+		.proc_handler = &proc_dointvec,
+	},
+	{ .ctl_name = 0 }
+};