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Commit ddb99e11 authored by Elena Reshetova's avatar Elena Reshetova Committed by James Morris
Browse files

security, keys: convert key_user.usage from atomic_t to refcount_t 



refcount_t type and corresponding API should be
used instead of atomic_t when the variable is used as
a reference counter. This allows to avoid accidental
refcounter overflows that might lead to use-after-free
situations.

Signed-off-by: default avatarElena Reshetova <elena.reshetova@intel.com>
Signed-off-by: default avatarHans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: default avatarKees Cook <keescook@chromium.org>
Signed-off-by: default avatarDavid Windsor <dwindsor@gmail.com>
Acked-by: default avatarDavid Howells <dhowells@redhat.com>
Signed-off-by: default avatarJames Morris <james.l.morris@oracle.com>
parent fff29291

security/keys/internal.h

+2 −1
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <linux/key-type.h>

#include <linux/task_work.h>

#include <linux/keyctl.h>

#include <linux/refcount.h>



struct iovec;
@@ -53,7 +54,7 @@ struct key_user { 
	struct rb_node		node;

	struct mutex		cons_lock;	/* construction initiation lock */

	spinlock_t		lock;

	atomic_t		usage;		/* for accessing qnkeys & qnbytes */

	refcount_t		usage;		/* for accessing qnkeys & qnbytes */

	atomic_t		nkeys;		/* number of keys */

	atomic_t		nikeys;		/* number of instantiated keys */

	kuid_t			uid;

security/keys/key.c

+3 −3
Original line number Diff line number Diff line
@@ -93,7 +93,7 @@ struct key_user *key_user_lookup(kuid_t uid) 


	/* if we get here, then the user record still hadn't appeared on the

	 * second pass - so we use the candidate record */

	atomic_set(&candidate->usage, 1);

	refcount_set(&candidate->usage, 1);

	atomic_set(&candidate->nkeys, 0);

	atomic_set(&candidate->nikeys, 0);

	candidate->uid = uid;
@@ -110,7 +110,7 @@ struct key_user *key_user_lookup(kuid_t uid) 


	/* okay - we found a user record for this UID */

found:

	atomic_inc(&user->usage);

	refcount_inc(&user->usage);

	spin_unlock(&key_user_lock);

	kfree(candidate);

out:
@@ -122,7 +122,7 @@ struct key_user *key_user_lookup(kuid_t uid) 
 */

void key_user_put(struct key_user *user)

{

	if (atomic_dec_and_lock(&user->usage, &key_user_lock)) {

	if (refcount_dec_and_lock(&user->usage, &key_user_lock)) {

		rb_erase(&user->node, &key_user_tree);

		spin_unlock(&key_user_lock);

security/keys/proc.c

+1 −1
Original line number Diff line number Diff line
@@ -340,7 +340,7 @@ static int proc_key_users_show(struct seq_file *m, void *v) 


	seq_printf(m, "%5u: %5d %d/%d %d/%d %d/%d\n",

		   from_kuid_munged(seq_user_ns(m), user->uid),

		   atomic_read(&user->usage),

		   refcount_read(&user->usage),

		   atomic_read(&user->nkeys),

		   atomic_read(&user->nikeys),

		   user->qnkeys,

security/keys/process_keys.c

+1 −1
Original line number Diff line number Diff line
@@ -30,7 +30,7 @@ static DEFINE_MUTEX(key_user_keyring_mutex); 


/* The root user's tracking struct */

struct key_user root_key_user = {

	.usage		= ATOMIC_INIT(3),

	.usage		= REFCOUNT_INIT(3),

	.cons_lock	= __MUTEX_INITIALIZER(root_key_user.cons_lock),

	.lock		= __SPIN_LOCK_UNLOCKED(root_key_user.lock),

	.nkeys		= ATOMIC_INIT(2),