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

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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: Elena Reshetova <elena.reshetova@intel.com>
Signed-off-by: Hans Liljestrand <ishkamiel@gmail.com>
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: David Windsor <dwindsor@gmail.com>
Acked-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
This commit is contained in:
Elena Reshetova
2017-03-31 15:20:49 +03:00
committed by James Morris
parent fff292914d
commit ddb99e118e
4 changed files with 7 additions and 6 deletions
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6
security/keys/key.c
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@@ -93,7 +93,7 @@ try_again:
/* 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 @@ try_again:
/* 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 @@ out:
*/
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);