On Tue, Dec 01, 2015 at 05:46:40PM -0500, Chas Williams wrote: > From: David Howells <dhowells@xxxxxxxxxx> > > 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. > > Fixes CVE-2015-7872. > > Reported-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > Signed-off-by: David Howells <dhowells@xxxxxxxxxx> > Tested-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx> > [3chas3@xxxxxxxxx: backported to 4.1 due to context changes] I took an earlier keys patch as well, which didn't require this context change, but thanks for the backport. greg k-h -- To unsubscribe from this list: send the line "unsubscribe stable" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html