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Date: Mon, 23 Nov 2015 14:12:24 +0100 From: Jiri Slaby <jslaby@...e.cz> To: stable@...r.kernel.org Cc: linux-kernel@...r.kernel.org, David Howells <dhowells@...hat.com>, Jiri Slaby <jslaby@...e.cz> Subject: [PATCH 3.12 63/72] KEYS: Fix race between key destruction and finding a keyring by name From: David Howells <dhowells@...hat.com> 3.12-stable review patch. If anyone has any objections, please let me know. =============== 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@...hat.com> Signed-off-by: David Howells <dhowells@...hat.com> Signed-off-by: Jiri Slaby <jslaby@...e.cz> --- 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 797818695c87..483ebdf9c383 100644 --- a/security/keys/gc.c +++ b/security/keys/gc.c @@ -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); -- 2.6.3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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