On Thu, Oct 15, 2015 at 9:21 PM, David Howells <dhowe...@redhat.com> wrote:
> Does the attached patch fix it for you?
Yes, it fixes the crash for me.
> David
> ---
> commit a7609e0bb3973d6ee3c9f1ecd0b6a382d99d6248
> Author: David Howells <dhowe...@redhat.com>
> Date: Thu Oct 15 17:21:37 2015 +0100
>
> 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 <dvyu...@google.com>
> Signed-off-by: David Howells <dhowe...@redhat.com>
>
> 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);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
