| From f05819df10d7b09f6d1eb6f8534a8f68e5a4fe61 Mon Sep 17 00:00:00 2001 |
| From: David Howells <dhowells@redhat.com> |
| Date: Thu, 15 Oct 2015 17:21:37 +0100 |
| Subject: KEYS: Fix crash when attempt to garbage collect an uninstantiated |
| keyring |
| |
| commit f05819df10d7b09f6d1eb6f8534a8f68e5a4fe61 upstream. |
| |
| 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> |
| [lizf: Backported to 3.4: adjust indentation] |
| Signed-off-by: Zefan Li <lizefan@huawei.com> |
| --- |
| security/keys/gc.c | 6 ++++-- |
| 1 file changed, 4 insertions(+), 2 deletions(-) |
| |
| --- a/security/keys/gc.c |
| +++ b/security/keys/gc.c |
| @@ -174,8 +174,10 @@ static noinline void key_gc_unused_key(s |
| { |
| 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); |