| From | Luis Henriques <> | Subject | [PATCH 3.16.y-ckt 105/107] KEYS: Fix race between key destruction and finding a keyring by name | Date | Mon, 26 Oct 2015 19:05:27 +0000 |
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3.16.7-ckt19 -stable review patch. If anyone has any objections, please let me know.
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From: David Howells <dhowells@redhat.com>
commit 94c4554ba07adbdde396748ee7ae01e86cf2d8d7 upstream.
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.
Reported-by: Petr Matousek <pmatouse@redhat.com> Signed-off-by: David Howells <dhowells@redhat.com> Cc: Kamal Mostafa <kamal@canonical.com> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- security/keys/gc.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/security/keys/gc.c b/security/keys/gc.c index 009d9370c8fd..38676fac7943 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -143,6 +143,10 @@ 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 */ @@ -157,10 +161,6 @@ 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);
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