Re: [PATCH 6/7] keys: Add a keyctl to move a key between keyrings
From: Eric Biggers
Date: Wed May 29 2019 - 19:28:42 EST
On Wed, May 22, 2019 at 11:28:45PM +0100, David Howells wrote:
> Add a keyctl to atomically move a link to a key from one keyring to
> another. The key must exist in "from" keyring and a flag can be given to
> cause the operation to fail if there's a matching key already in the "to"
> keyring.
>
> This can be done with:
>
> keyctl(KEYCTL_MOVE,
> key_serial_t key,
> key_serial_t from_keyring,
> key_serial_t to_keyring,
> unsigned int flags);
>
> The key being moved must grant Link permission and both keyrings must grant
> Write permission.
>
> flags should be 0 or KEYCTL_MOVE_EXCL, with the latter preventing
> displacement of a matching key from the "to" keyring.
>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
This shows up after a few seconds of syzkaller fuzzing with a description of
KEYCTL_MOVE added:
WARNING: possible circular locking dependency detected
5.2.0-rc1 #5 Not tainted
------------------------------------------------------
syz-executor.28/27700 is trying to acquire lock:
00000000049888d8 (keyring_serialise_link_sem){+.+.}, at: __key_link_begin+0x1c2/0x2d0 security/keys/keyring.c:1231
but task is already holding lock:
00000000b171310c (&type->lock_class/1){+.+.}, at: __key_link_begin+0xa4/0x2d0 security/keys/keyring.c:1222
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&type->lock_class/1){+.+.}:
lock_acquire+0x106/0x330 kernel/locking/lockdep.c:4302
down_write_nested+0x3c/0xa0 kernel/locking/rwsem.c:177
__key_unlink_begin+0x6c/0x110 security/keys/keyring.c:1398
key_move+0x3ad/0x470 security/keys/keyring.c:1538
keyctl_keyring_move+0xb6/0x120 security/keys/keyctl.c:610
__do_sys_keyctl security/keys/keyctl.c:1823 [inline]
__se_sys_keyctl+0x8e/0x2c0 security/keys/keyctl.c:1685
__x64_sys_keyctl+0xbe/0x150 security/keys/keyctl.c:1685
do_syscall_64+0x9e/0x4b0 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
-> #0 (keyring_serialise_link_sem){+.+.}:
check_prevs_add kernel/locking/lockdep.c:2417 [inline]
validate_chain kernel/locking/lockdep.c:2799 [inline]
__lock_acquire+0x38a4/0x3c30 kernel/locking/lockdep.c:3792
lock_acquire+0x106/0x330 kernel/locking/lockdep.c:4302
down_write+0x38/0xa0 kernel/locking/rwsem.c:66
__key_link_begin+0x1c2/0x2d0 security/keys/keyring.c:1231
key_move+0xf0/0x470 security/keys/keyring.c:1529
keyctl_keyring_move+0xb6/0x120 security/keys/keyctl.c:610
__do_sys_keyctl security/keys/keyctl.c:1823 [inline]
__se_sys_keyctl+0x8e/0x2c0 security/keys/keyctl.c:1685
__x64_sys_keyctl+0xbe/0x150 security/keys/keyctl.c:1685
do_syscall_64+0x9e/0x4b0 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&type->lock_class/1);
lock(keyring_serialise_link_sem);
lock(&type->lock_class/1);
lock(keyring_serialise_link_sem);
*** DEADLOCK ***
2 locks held by syz-executor.28/27700:
#0: 000000002a03f208 (&type->lock_class){++++}, at: __key_unlink_begin+0x6c/0x110 security/keys/keyring.c:1398
#1: 00000000b171310c (&type->lock_class/1){+.+.}, at: __key_link_begin+0xa4/0x2d0 security/keys/keyring.c:1222
stack backtrace:
CPU: 8 PID: 27700 Comm: syz-executor.28 Not tainted 5.2.0-rc1 #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0xb1/0x118 lib/dump_stack.c:113
print_circular_bug+0x4a4/0x4b5 kernel/locking/lockdep.c:1564
check_prev_add+0xd1f/0x1af7 kernel/locking/lockdep.c:2309
check_prevs_add kernel/locking/lockdep.c:2417 [inline]
validate_chain kernel/locking/lockdep.c:2799 [inline]
__lock_acquire+0x38a4/0x3c30 kernel/locking/lockdep.c:3792
lock_acquire+0x106/0x330 kernel/locking/lockdep.c:4302
down_write+0x38/0xa0 kernel/locking/rwsem.c:66
__key_link_begin+0x1c2/0x2d0 security/keys/keyring.c:1231
key_move+0xf0/0x470 security/keys/keyring.c:1529
keyctl_keyring_move+0xb6/0x120 security/keys/keyctl.c:610
__do_sys_keyctl security/keys/keyctl.c:1823 [inline]
__se_sys_keyctl+0x8e/0x2c0 security/keys/keyctl.c:1685
__x64_sys_keyctl+0xbe/0x150 security/keys/keyctl.c:1685
do_syscall_64+0x9e/0x4b0 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458a09
Code: dd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 ab b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f9d53755c88 EFLAGS: 00000246 ORIG_RAX: 00000000000000fa
RAX: ffffffffffffffda RBX: 000000000071bf00 RCX: 0000000000458a09
RDX: 000000001f62d16e RSI: 000000002490e642 RDI: 000000000000001e
RBP: 00007f9d53755ca0 R08: 0000000000000000 R09: 0000000000000000
R10: 000000001afbc80a R11: 0000000000000246 R12: 00007f9d537566d4
R13: 00000000004ac12c R14: 00000000006ebd68 R15: 0000000000000003
FAULT_INJECTION: forcing a failure.
name failslab, interval 1, probability 0, space 0, times 0
CPU: 8 PID: 27700 Comm: syz-executor.28 Not tainted 5.2.0-rc1 #5
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0xb1/0x118 lib/dump_stack.c:113
fail_dump lib/fault-inject.c:51 [inline]
should_fail+0x61e/0x720 lib/fault-inject.c:143
__should_failslab+0xec/0x120 mm/failslab.c:32
should_failslab+0x9/0x14 mm/slab_common.c:1610
slab_pre_alloc_hook mm/slab.h:420 [inline]
slab_alloc mm/slab.c:3312 [inline]
kmem_cache_alloc_trace+0x146/0x2a0 mm/slab.c:3553
kmalloc include/linux/slab.h:547 [inline]
kzalloc include/linux/slab.h:742 [inline]
assoc_array_insert+0xcc/0x440 lib/assoc_array.c:985
__key_link_begin+0x120/0x2d0 security/keys/keyring.c:1236
key_move+0xf0/0x470 security/keys/keyring.c:1529
keyctl_keyring_move+0xb6/0x120 security/keys/keyctl.c:610
__do_sys_keyctl security/keys/keyctl.c:1823 [inline]
__se_sys_keyctl+0x8e/0x2c0 security/keys/keyctl.c:1685
__x64_sys_keyctl+0xbe/0x150 security/keys/keyctl.c:1685
do_syscall_64+0x9e/0x4b0 arch/x86/entry/common.c:301
entry_SYSCALL_64_after_hwframe+0x49/0xbe
RIP: 0033:0x458a09
Code: dd b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00 00 66 90 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 0f 83 ab b4 fb ff c3 66 2e 0f 1f 84 00 00 00 00
RSP: 002b:00007f9d53755c88 EFLAGS: 00000246 ORIG_RAX: 00000000000000fa
RAX: ffffffffffffffda RBX: 000000000071bf00 RCX: 0000000000458a09
RDX: 000000001f62d16e RSI: 000000002490e642 RDI: 000000000000001e
RBP: 00007f9d53755ca0 R08: 0000000000000000 R09: 0000000000000000
R10: 000000001afbc80a R11: 0000000000000246 R12: 00007f9d537566d4
R13: 00000000004ac12c R14: 00000000006ebd68 R15: 0000000000000003