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authorDavid Howells <dhowells@redhat.com>2015-10-15 17:21:37 +0100
committerDavid Howells <dhowells@redhat.com>2015-10-15 17:21:37 +0100
commitf05819df10d7b09f6d1eb6f8534a8f68e5a4fe61 (patch)
treeb7e30f6dd071b630bd888894eab5b216a5f53766
parent5b5f1455272e23f4e7889cec37228802d8d01adf (diff)
KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring
The following sequence of commands: i=`keyctl add user a a @s` keyctl request2 keyring foo bar @t keyctl unlink $i @s tries to invoke an upcall to instantiate a keyring if one doesn't already exist by that name within the user's keyring set. However, if the upcall fails, the code sets keyring->type_data.reject_error to -ENOKEY or some other error code. When the key is garbage collected, the key destroy function is called unconditionally and keyring_destroy() uses list_empty() on keyring->type_data.link - which is in a union with reject_error. Subsequently, the kernel tries to unlink the keyring from the keyring names list - which oopses like this: BUG: unable to handle kernel paging request at 00000000ffffff8a IP: [<ffffffff8126e051>] keyring_destroy+0x3d/0x88 ... Workqueue: events key_garbage_collector ... RIP: 0010:[<ffffffff8126e051>] keyring_destroy+0x3d/0x88 RSP: 0018:ffff88003e2f3d30 EFLAGS: 00010203 RAX: 00000000ffffff82 RBX: ffff88003bf1a900 RCX: 0000000000000000 RDX: 0000000000000000 RSI: 000000003bfc6901 RDI: ffffffff81a73a40 RBP: ffff88003e2f3d38 R08: 0000000000000152 R09: 0000000000000000 R10: ffff88003e2f3c18 R11: 000000000000865b R12: ffff88003bf1a900 R13: 0000000000000000 R14: ffff88003bf1a908 R15: ffff88003e2f4000 ... CR2: 00000000ffffff8a CR3: 000000003e3ec000 CR4: 00000000000006f0 ... Call Trace: [<ffffffff8126c756>] key_gc_unused_keys.constprop.1+0x5d/0x10f [<ffffffff8126ca71>] key_garbage_collector+0x1fa/0x351 [<ffffffff8105ec9b>] process_one_work+0x28e/0x547 [<ffffffff8105fd17>] worker_thread+0x26e/0x361 [<ffffffff8105faa9>] ? rescuer_thread+0x2a8/0x2a8 [<ffffffff810648ad>] kthread+0xf3/0xfb [<ffffffff810647ba>] ? kthread_create_on_node+0x1c2/0x1c2 [<ffffffff815f2ccf>] ret_from_fork+0x3f/0x70 [<ffffffff810647ba>] ? kthread_create_on_node+0x1c2/0x1c2 Note the value in RAX. This is a 32-bit representation of -ENOKEY. The solution is to only call ->destroy() if the key was successfully instantiated. Reported-by: Dmitry Vyukov <dvyukov@google.com> Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Dmitry Vyukov <dvyukov@google.com>
-rw-r--r--security/keys/gc.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/security/keys/gc.c b/security/keys/gc.c
index 39eac1fd5706..addf060399e0 100644
--- a/security/keys/gc.c
+++ b/security/keys/gc.c
@@ -134,8 +134,10 @@ 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)
+ /* Throw away the key data if the key is instantiated */
+ if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags) &&
+ !test_bit(KEY_FLAG_NEGATIVE, &key->flags) &&
+ key->type->destroy)
key->type->destroy(key);
security_key_free(key);