linux/security/keys
David Howells 096fe9eaea KEYS: Fix handling of stored error in a negatively instantiated user key
If a user key gets negatively instantiated, an error code is cached in the
payload area.  A negatively instantiated key may be then be positively
instantiated by updating it with valid data.  However, the ->update key
type method must be aware that the error code may be there.

The following may be used to trigger the bug in the user key type:

    keyctl request2 user user "" @u
    keyctl add user user "a" @u

which manifests itself as:

	BUG: unable to handle kernel paging request at 00000000ffffff8a
	IP: [<ffffffff810a376f>] __call_rcu.constprop.76+0x1f/0x280 kernel/rcu/tree.c:3046
	PGD 7cc30067 PUD 0
	Oops: 0002 [#1] SMP
	Modules linked in:
	CPU: 3 PID: 2644 Comm: a.out Not tainted 4.3.0+ #49
	Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011
	task: ffff88003ddea700 ti: ffff88003dd88000 task.ti: ffff88003dd88000
	RIP: 0010:[<ffffffff810a376f>]  [<ffffffff810a376f>] __call_rcu.constprop.76+0x1f/0x280
	 [<ffffffff810a376f>] __call_rcu.constprop.76+0x1f/0x280 kernel/rcu/tree.c:3046
	RSP: 0018:ffff88003dd8bdb0  EFLAGS: 00010246
	RAX: 00000000ffffff82 RBX: 0000000000000000 RCX: 0000000000000001
	RDX: ffffffff81e3fe40 RSI: 0000000000000000 RDI: 00000000ffffff82
	RBP: ffff88003dd8bde0 R08: ffff88007d2d2da0 R09: 0000000000000000
	R10: 0000000000000000 R11: ffff88003e8073c0 R12: 00000000ffffff82
	R13: ffff88003dd8be68 R14: ffff88007d027600 R15: ffff88003ddea700
	FS:  0000000000b92880(0063) GS:ffff88007fd00000(0000) knlGS:0000000000000000
	CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
	CR2: 00000000ffffff8a CR3: 000000007cc5f000 CR4: 00000000000006e0
	Stack:
	 ffff88003dd8bdf0 ffffffff81160a8a 0000000000000000 00000000ffffff82
	 ffff88003dd8be68 ffff88007d027600 ffff88003dd8bdf0 ffffffff810a39e5
	 ffff88003dd8be20 ffffffff812a31ab ffff88007d027600 ffff88007d027620
	Call Trace:
	 [<ffffffff810a39e5>] kfree_call_rcu+0x15/0x20 kernel/rcu/tree.c:3136
	 [<ffffffff812a31ab>] user_update+0x8b/0xb0 security/keys/user_defined.c:129
	 [<     inline     >] __key_update security/keys/key.c:730
	 [<ffffffff8129e5c1>] key_create_or_update+0x291/0x440 security/keys/key.c:908
	 [<     inline     >] SYSC_add_key security/keys/keyctl.c:125
	 [<ffffffff8129fc21>] SyS_add_key+0x101/0x1e0 security/keys/keyctl.c:60
	 [<ffffffff8185f617>] entry_SYSCALL_64_fastpath+0x12/0x6a arch/x86/entry/entry_64.S:185

Note the error code (-ENOKEY) in EDX.

A similar bug can be tripped by:

    keyctl request2 trusted user "" @u
    keyctl add trusted user "a" @u

This should also affect encrypted keys - but that has to be correctly
parameterised or it will fail with EINVAL before getting to the bit that
will crashes.

Reported-by: Dmitry Vyukov <dvyukov@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: James Morris <james.l.morris@oracle.com>
2015-11-25 14:19:47 +11:00
..
encrypted-keys KEYS: Fix handling of stored error in a negatively instantiated user key 2015-11-25 14:19:47 +11:00
Kconfig KEYS: Make /proc/keys unconditional if CONFIG_KEYS=y 2015-01-22 22:34:32 +00:00
Makefile KEYS: Add per-user_namespace registers for persistent per-UID kerberos caches 2013-09-24 10:35:19 +01:00
big_key.c KEYS: Merge the type-specific data with the payload data 2015-10-21 15:18:36 +01:00
compat.c switch keyctl_instantiate_key_common() to iov_iter 2015-04-11 22:27:12 -04:00
gc.c KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring 2015-10-15 17:21:37 +01:00
internal.h switch keyctl_instantiate_key_common() to iov_iter 2015-04-11 22:27:12 -04:00
key.c KEYS: Merge the type-specific data with the payload data 2015-10-21 15:18:36 +01:00
keyctl.c KEYS: Merge the type-specific data with the payload data 2015-10-21 15:18:36 +01:00
keyring.c KEYS: Merge the type-specific data with the payload data 2015-10-21 15:18:36 +01:00
permission.c KEYS: Move the flags representing required permission to linux/key.h 2014-03-14 17:44:49 +00:00
persistent.c KEYS: Move the flags representing required permission to linux/key.h 2014-03-14 17:44:49 +00:00
proc.c KEYS: Make /proc/keys unconditional if CONFIG_KEYS=y 2015-01-22 22:34:32 +00:00
process_keys.c KEYS: Merge the type-specific data with the payload data 2015-10-21 15:18:36 +01:00
request_key.c Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security 2015-11-05 15:32:38 -08:00
request_key_auth.c KEYS: Merge the type-specific data with the payload data 2015-10-21 15:18:36 +01:00
sysctl.c security: Convert use of typedef ctl_table to struct ctl_table 2014-04-15 13:39:58 +10:00
trusted.c KEYS: Fix handling of stored error in a negatively instantiated user key 2015-11-25 14:19:47 +11:00
trusted.h keys, trusted: move struct trusted_key_options to trusted-type.h 2015-10-19 01:01:21 +02:00
user_defined.c KEYS: Fix handling of stored error in a negatively instantiated user key 2015-11-25 14:19:47 +11:00