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KEYS: Fix race between key destruction and finding a keyring by name

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There appears to be a race between:

 (1) key_gc_unused_keys() which frees key->security and then calls
     keyring_destroy() to unlink the name from the name list

 (2) find_keyring_by_name() which calls key_permission(), thus accessing
     key->security, on a key before checking to see whether the key usage is 0
     (ie. the key is dead and might be cleaned up).

Fix this by calling ->destroy() before cleaning up the core key data -
including key->security.

Change-Id: I4b9b89af020e6348af095e9014bf23b5eb1a9ef9
Reported-by: Petr Matousek <pmatouse@redhat.com>
Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2015-09-25 16:30:08 +01:00 committed by Zhao Wei Liew
parent 62b1b19ca5
commit 0e7ea8aab9
1 changed files with 4 additions and 4 deletions
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8
security/keys/gc.c
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@ -187,6 +187,10 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
kdebug("- %u", key->serial);
key_check(key);
/* Throw away the key data */
if (key->type->destroy)
key->type->destroy(key);
security_key_free(key);
/* deal with the user's key tracking and quota */
@ -201,10 +205,6 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
atomic_dec(&key->user->nikeys);
/* now throw away the key memory */
if (key->type->destroy)
key->type->destroy(key);
key_user_put(key->user);
kfree(key->description);