kernel/linux.git/security/keys/key.c, branch v4.12.9

KEYS: fix refcount_inc() on zero

2017-06-09T03:29:50+00:00

If a key's refcount is dropped to zero between key_lookup() peeking at the refcount and subsequently attempting to increment it, refcount_inc() will see a zero refcount. Here, refcount_inc() will WARN_ONCE(), and will *not* increment the refcount, which will remain zero. Once key_lookup() drops key_serial_lock, it is possible for the key to be freed behind our back. This patch uses refcount_inc_not_zero() to perform the peek and increment atomically. Fixes: fff292914d3a2f1e ("security, keys: convert key.usage from atomic_t to refcount_t") Signed-off-by: Mark Rutland Signed-off-by: David Howells Cc: David Windsor Cc: Elena Reshetova Cc: Hans Liljestrand Cc: James Morris Cc: Kees Cook Cc: Peter Zijlstra Signed-off-by: James Morris

KEYS: fix freeing uninitialized memory in key_update()

2017-06-09T03:29:47+00:00

key_update() freed the key_preparsed_payload even if it was not initialized first. This would cause a crash if userspace called keyctl_update() on a key with type like "asymmetric" that has a ->preparse() method but not an ->update() method. Possibly it could even be triggered for other key types by racing with keyctl_setperm() to make the KEY_NEED_WRITE check fail (the permission was already checked, so normally it wouldn't fail there). Reproducer with key type "asymmetric", given a valid cert.der: keyctl new_session keyid=$(keyctl padd asymmetric desc @s < cert.der) keyctl setperm $keyid 0x3f000000 keyctl update $keyid data [ 150.686666] BUG: unable to handle kernel NULL pointer dereference at 0000000000000001 [ 150.687601] IP: asymmetric_key_free_kids+0x12/0x30 [ 150.688139] PGD 38a3d067 [ 150.688141] PUD 3b3de067 [ 150.688447] PMD 0 [ 150.688745] [ 150.689160] Oops: 0000 [#1] SMP [ 150.689455] Modules linked in: [ 150.689769] CPU: 1 PID: 2478 Comm: keyctl Not tainted 4.11.0-rc4-xfstests-00187-ga9f6b6b8cd2f #742 [ 150.690916] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-20170228_101828-anatol 04/01/2014 [ 150.692199] task: ffff88003b30c480 task.stack: ffffc90000350000 [ 150.692952] RIP: 0010:asymmetric_key_free_kids+0x12/0x30 [ 150.693556] RSP: 0018:ffffc90000353e58 EFLAGS: 00010202 [ 150.694142] RAX: 0000000000000000 RBX: 0000000000000001 RCX: 0000000000000004 [ 150.694845] RDX: ffffffff81ee3920 RSI: ffff88003d4b0700 RDI: 0000000000000001 [ 150.697569] RBP: ffffc90000353e60 R08: ffff88003d5d2140 R09: 0000000000000000 [ 150.702483] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000001 [ 150.707393] R13: 0000000000000004 R14: ffff880038a4d2d8 R15: 000000000040411f [ 150.709720] FS: 00007fcbcee35700(0000) GS:ffff88003fd00000(0000) knlGS:0000000000000000 [ 150.711504] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 150.712733] CR2: 0000000000000001 CR3: 0000000039eab000 CR4: 00000000003406e0 [ 150.714487] Call Trace: [ 150.714975] asymmetric_key_free_preparse+0x2f/0x40 [ 150.715907] key_update+0xf7/0x140 [ 150.716560] ? key_default_cmp+0x20/0x20 [ 150.717319] keyctl_update_key+0xb0/0xe0 [ 150.718066] SyS_keyctl+0x109/0x130 [ 150.718663] entry_SYSCALL_64_fastpath+0x1f/0xc2 [ 150.719440] RIP: 0033:0x7fcbce75ff19 [ 150.719926] RSP: 002b:00007ffd5d167088 EFLAGS: 00000206 ORIG_RAX: 00000000000000fa [ 150.720918] RAX: ffffffffffffffda RBX: 0000000000404d80 RCX: 00007fcbce75ff19 [ 150.721874] RDX: 00007ffd5d16785e RSI: 000000002866cd36 RDI: 0000000000000002 [ 150.722827] RBP: 0000000000000006 R08: 000000002866cd36 R09: 00007ffd5d16785e [ 150.723781] R10: 0000000000000004 R11: 0000000000000206 R12: 0000000000404d80 [ 150.724650] R13: 00007ffd5d16784d R14: 00007ffd5d167238 R15: 000000000040411f [ 150.725447] Code: 83 c4 08 31 c0 5b 41 5c 41 5d 41 5e 41 5f 5d c3 66 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 48 85 ff 74 23 55 48 89 e5 53 48 89 fb <48> 8b 3f e8 06 21 c5 ff 48 8b 7b 08 e8 fd 20 c5 ff 48 89 df e8 [ 150.727489] RIP: asymmetric_key_free_kids+0x12/0x30 RSP: ffffc90000353e58 [ 150.728117] CR2: 0000000000000001 [ 150.728430] ---[ end trace f7f8fe1da2d5ae8d ]--- Fixes: 4d8c0250b841 ("KEYS: Call ->free_preparse() even after ->preparse() returns an error") Cc: stable@vger.kernel.org # 3.17+ Signed-off-by: Eric Biggers Signed-off-by: David Howells Signed-off-by: James Morris

KEYS: Consistent ordering for __key_link_begin and restrict check

2017-04-04T21:10:11+00:00

The keyring restrict callback was sometimes called before __key_link_begin and sometimes after, which meant that the keyring semaphores were not always held during the restrict callback. If the semaphores are consistently acquired before checking link restrictions, keyring contents cannot be changed after the restrict check is complete but before the evaluated key is linked to the keyring. Signed-off-by: Mat Martineau

KEYS: Use structure to capture key restriction function and data

2017-04-04T21:10:10+00:00

Replace struct key's restrict_link function pointer with a pointer to the new struct key_restriction. The structure contains pointers to the restriction function as well as relevant data for evaluating the restriction. The garbage collector checks restrict_link->keytype when key types are unregistered. Restrictions involving a removed key type are converted to use restrict_link_reject so that restrictions cannot be removed by unregistering key types. Signed-off-by: Mat Martineau

KEYS: Split role of the keyring pointer for keyring restrict functions

2017-04-03T17:24:56+00:00

The first argument to the restrict_link_func_t functions was a keyring pointer. These functions are called by the key subsystem with this argument set to the destination keyring, but restrict_link_by_signature expects a pointer to the relevant trusted keyring. Restrict functions may need something other than a single struct key pointer to allow or reject key linkage, so the data used to make that decision (such as the trust keyring) is moved to a new, fourth argument. The first argument is now always the destination keyring. Signed-off-by: Mat Martineau

KEYS: Use a typedef for restrict_link function pointers

2017-04-03T17:24:55+00:00

This pointer type needs to be returned from a lookup function, and without a typedef the syntax gets cumbersome. Signed-off-by: Mat Martineau

security, keys: convert key_user.usage from atomic_t to refcount_t

2017-04-03T00:49:06+00:00

refcount_t type and corresponding API should be used instead of atomic_t when the variable is used as a reference counter. This allows to avoid accidental refcounter overflows that might lead to use-after-free situations. Signed-off-by: Elena Reshetova Signed-off-by: Hans Liljestrand Signed-off-by: Kees Cook Signed-off-by: David Windsor Acked-by: David Howells Signed-off-by: James Morris

security, keys: convert key.usage from atomic_t to refcount_t

2017-04-03T00:49:05+00:00

KEYS: potential uninitialized variable

2016-06-17T03:15:04+00:00

If __key_link_begin() failed then "edit" would be uninitialized. I've added a check to fix that. This allows a random user to crash the kernel, though it's quite difficult to achieve. There are three ways it can be done as the user would have to cause an error to occur in __key_link(): (1) Cause the kernel to run out of memory. In practice, this is difficult to achieve without ENOMEM cropping up elsewhere and aborting the attempt. (2) Revoke the destination keyring between the keyring ID being looked up and it being tested for revocation. In practice, this is difficult to time correctly because the KEYCTL_REJECT function can only be used from the request-key upcall process. Further, users can only make use of what's in /sbin/request-key.conf, though this does including a rejection debugging test - which means that the destination keyring has to be the caller's session keyring in practice. (3) Have just enough key quota available to create a key, a new session keyring for the upcall and a link in the session keyring, but not then sufficient quota to create a link in the nominated destination keyring so that it fails with EDQUOT. The bug can be triggered using option (3) above using something like the following: echo 80 >/proc/sys/kernel/keys/root_maxbytes keyctl request2 user debug:fred negate @t The above sets the quota to something much lower (80) to make the bug easier to trigger, but this is dependent on the system. Note also that the name of the keyring created contains a random number that may be between 1 and 10 characters in size, so may throw the test off by changing the amount of quota used. Assuming the failure occurs, something like the following will be seen: kfree_debugcheck: out of range ptr 6b6b6b6b6b6b6b68h ------------[ cut here ]------------ kernel BUG at ../mm/slab.c:2821! ... RIP: 0010:[] kfree_debugcheck+0x20/0x25 RSP: 0018:ffff8804014a7de8 EFLAGS: 00010092 RAX: 0000000000000034 RBX: 6b6b6b6b6b6b6b68 RCX: 0000000000000000 RDX: 0000000000040001 RSI: 00000000000000f6 RDI: 0000000000000300 RBP: ffff8804014a7df0 R08: 0000000000000001 R09: 0000000000000000 R10: ffff8804014a7e68 R11: 0000000000000054 R12: 0000000000000202 R13: ffffffff81318a66 R14: 0000000000000000 R15: 0000000000000001 ... Call Trace: kfree+0xde/0x1bc assoc_array_cancel_edit+0x1f/0x36 __key_link_end+0x55/0x63 key_reject_and_link+0x124/0x155 keyctl_reject_key+0xb6/0xe0 keyctl_negate_key+0x10/0x12 SyS_keyctl+0x9f/0xe7 do_syscall_64+0x63/0x13a entry_SYSCALL64_slow_path+0x25/0x25 Fixes: f70e2e06196a ('KEYS: Do preallocation for __key_link()') Signed-off-by: Dan Carpenter Signed-off-by: David Howells cc: stable@vger.kernel.org Signed-off-by: Linus Torvalds

KEYS: Remove KEY_FLAG_TRUSTED and KEY_ALLOC_TRUSTED

2016-04-11T21:44:15+00:00

Remove KEY_FLAG_TRUSTED and KEY_ALLOC_TRUSTED as they're no longer meaningful. Also we can drop the trusted flag from the preparse structure. Given this, we no longer need to pass the key flags through to restrict_link(). Further, we can now get rid of keyring_restrict_trusted_only() also. Signed-off-by: David Howells