Patch "KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring" has been added to the 3.10-stable tree
Subsystems (3)
This is a note to let you know that I've just added the patch titled
KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
keys-fix-crash-when-attempt-to-garbage-collect-an-uninstantiated-keyring.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.
Quoted 1 line
From
f05819df10d7b09f6d1eb6f8534a8f68e5a4fe61Mon Sep 17 00:00:00 2001
From: David Howells <[email protected]>
Date: Thu, 15 Oct 2015 17:21:37 +0100
Subject: KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring
From: David Howells <[email protected]>
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.
--- security/keys/gc.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)
security/keys/gc.c +4 -2
@@ -187,8 +187,10 @@ static noinline void key_gc_unused_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);
Patches currently in stable-queue which might be from [email protected] are
queue-3.10/keys-fix-keyring-ref-leak-in-join_session_keyring.patch queue-3.10/keys-fix-crash-when-attempt-to-garbage-collect-an-uninstantiated-keyring.patch queue-3.10/keys-fix-race-between-read-and-revoke.patch queue-3.10/keys-fix-race-between-key-destruction-and-finding-a-keyring-by-name.patch queue-3.10/keys-refcount-bug-fix.patch queue-3.10/keys-prevent-keys-from-being-removed-from-specified-keyrings.patch