diff options
Diffstat (limited to 'KEYS-don-t-let-add_key-update-an-uninstantiated-key.patch')
| -rw-r--r-- | KEYS-don-t-let-add_key-update-an-uninstantiated-key.patch | 130 |
1 files changed, 130 insertions, 0 deletions
diff --git a/KEYS-don-t-let-add_key-update-an-uninstantiated-key.patch b/KEYS-don-t-let-add_key-update-an-uninstantiated-key.patch new file mode 100644 index 000000000..af7478ee5 --- /dev/null +++ b/KEYS-don-t-let-add_key-update-an-uninstantiated-key.patch @@ -0,0 +1,130 @@ +From 7289bfaee2a42bdb56eecab0625907c045d080ba Mon Sep 17 00:00:00 2001 +From: Eric Biggers <ebiggers@google.com> +Date: Wed, 27 Sep 2017 12:50:41 -0700 +Subject: [PATCH] KEYS: don't let add_key() update an uninstantiated key + +Currently, add_key() will, when passed a key that already exists, call +the key's ->update() method. But this is heavily broken in the case +where the key is uninstantiated because it doesn't call +__key_instantiate_and_link(). Consequently, it doesn't do most of the +things that are supposed to happen when the key is instantiated, such as +setting KEY_FLAG_INSTANTIATED, clearing KEY_FLAG_USER_CONSTRUCT and +awakening tasks waiting on it, and incrementing key->user->nikeys. + +It also never takes key_construction_mutex, which means that +->instantiate() can run concurrently with ->update() on the same key. +In the case of the "user" and "logon" key types this causes a memory +leak, at best. Maybe even worse, the ->update() methods of the +"encrypted" and "trusted" key types actually just dereference a NULL +pointer when passed an uninstantiated key. + +Therefore, change find_key_to_update() to return NULL if the found key +is uninstantiated, so that add_key() replaces the key rather than +instantiating it. This seems to be better than fixing __key_update() to +call __key_instantiate_and_link(), since given all the bugs noted above +as well as that the existing behavior was undocumented and +keyctl_instantiate() is supposed to be used instead, I doubt anyone was +relying on the existing behavior. + +This patch only affects *uninstantiated* keys. For now we still allow a +negatively instantiated key to be updated (thereby positively +instantiating it), although that's broken too (the next patch fixes it) +and I'm not sure that anyone actually uses that functionality either. + +Here is a simple reproducer for the bug using the "encrypted" key type +(requires CONFIG_ENCRYPTED_KEYS=y), though as noted above the bug +pertained to more than just the "encrypted" key type: + + #include <stdlib.h> + #include <unistd.h> + #include <keyutils.h> + + int main(void) + { + int ringid = keyctl_join_session_keyring(NULL); + + if (fork()) { + for (;;) { + const char payload[] = "update user:foo 32"; + + usleep(rand() % 10000); + add_key("encrypted", "desc", payload, sizeof(payload), ringid); + keyctl_clear(ringid); + } + } else { + for (;;) + request_key("encrypted", "desc", "callout_info", ringid); + } + } + +It causes: + + BUG: unable to handle kernel NULL pointer dereference at 0000000000000018 + IP: encrypted_update+0xb0/0x170 + PGD 7a178067 P4D 7a178067 PUD 77269067 PMD 0 + PREEMPT SMP + CPU: 0 PID: 340 Comm: reproduce Tainted: G D 4.14.0-rc1-00025-g428490e38b2e #796 + Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Bochs 01/01/2011 + task: ffff8a467a39a340 task.stack: ffffb15c40770000 + RIP: 0010:encrypted_update+0xb0/0x170 + RSP: 0018:ffffb15c40773de8 EFLAGS: 00010246 + RAX: 0000000000000000 RBX: ffff8a467a275b00 RCX: 0000000000000000 + RDX: 0000000000000005 RSI: ffff8a467a275b14 RDI: ffffffffb742f303 + RBP: ffffb15c40773e20 R08: 0000000000000000 R09: ffff8a467a275b17 + R10: 0000000000000020 R11: 0000000000000000 R12: 0000000000000000 + R13: 0000000000000000 R14: ffff8a4677057180 R15: ffff8a467a275b0f + FS: 00007f5d7fb08700(0000) GS:ffff8a467f200000(0000) knlGS:0000000000000000 + CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 + CR2: 0000000000000018 CR3: 0000000077262005 CR4: 00000000001606f0 + Call Trace: + key_create_or_update+0x2bc/0x460 + SyS_add_key+0x10c/0x1d0 + entry_SYSCALL_64_fastpath+0x1f/0xbe + RIP: 0033:0x7f5d7f211259 + RSP: 002b:00007ffed03904c8 EFLAGS: 00000246 ORIG_RAX: 00000000000000f8 + RAX: ffffffffffffffda RBX: 000000003b2a7955 RCX: 00007f5d7f211259 + RDX: 00000000004009e4 RSI: 00000000004009ff RDI: 0000000000400a04 + RBP: 0000000068db8bad R08: 000000003b2a7955 R09: 0000000000000004 + R10: 000000000000001a R11: 0000000000000246 R12: 0000000000400868 + R13: 00007ffed03905d0 R14: 0000000000000000 R15: 0000000000000000 + Code: 77 28 e8 64 34 1f 00 45 31 c0 31 c9 48 8d 55 c8 48 89 df 48 8d 75 d0 e8 ff f9 ff ff 85 c0 41 89 c4 0f 88 84 00 00 00 4c 8b 7d c8 <49> 8b 75 18 4c 89 ff e8 24 f8 ff ff 85 c0 41 89 c4 78 6d 49 8b + RIP: encrypted_update+0xb0/0x170 RSP: ffffb15c40773de8 + CR2: 0000000000000018 + +Cc: <stable@vger.kernel.org> [v2.6.12+] +Signed-off-by: Eric Biggers <ebiggers@google.com> +--- + security/keys/keyring.c | 10 ++++++---- + 1 file changed, 6 insertions(+), 4 deletions(-) + +diff --git a/security/keys/keyring.c b/security/keys/keyring.c +index 4fa82a8a9c0e..129a4175760b 100644 +--- a/security/keys/keyring.c ++++ b/security/keys/keyring.c +@@ -1056,8 +1056,8 @@ EXPORT_SYMBOL(keyring_restrict); + * caller must also hold a lock on the keyring semaphore. + * + * Returns a pointer to the found key with usage count incremented if +- * successful and returns NULL if not found. Revoked and invalidated keys are +- * skipped over. ++ * successful and returns NULL if not found. Revoked, invalidated, and ++ * uninstantiated keys are skipped over. (But negative keys are not!) + * + * If successful, the possession indicator is propagated from the keyring ref + * to the returned key reference. +@@ -1084,8 +1084,10 @@ key_ref_t find_key_to_update(key_ref_t keyring_ref, + + found: + key = keyring_ptr_to_key(object); +- if (key->flags & ((1 << KEY_FLAG_INVALIDATED) | +- (1 << KEY_FLAG_REVOKED))) { ++ if ((key->flags & ((1 << KEY_FLAG_INVALIDATED) | ++ (1 << KEY_FLAG_REVOKED) | ++ (1 << KEY_FLAG_INSTANTIATED))) != ++ (1 << KEY_FLAG_INSTANTIATED)) { + kleave(" = NULL [x]"); + return NULL; + } +-- +2.13.6 + |