Fix crash in key garbage collector when using request_key (rhbz 1272172)
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Josh Boyer
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f904357bb7
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From e2293f0c696f863c3175c199b96de3711019352f Mon Sep 17 00:00:00 2001
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From: David Howells <dhowells@redhat.com>
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Date: Thu, 15 Oct 2015 17:21:37 +0100
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Subject: [PATCH 1/2] KEYS: Fix crash when attempt to garbage collect an
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uninstantiated keyring
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The following sequence of commands:
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i=`keyctl add user a a @s`
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keyctl request2 keyring foo bar @t
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keyctl unlink $i @s
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tries to invoke an upcall to instantiate a keyring if one doesn't already
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exist by that name within the user's keyring set. However, if the upcall
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fails, the code sets keyring->type_data.reject_error to -ENOKEY or some
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other error code. When the key is garbage collected, the key destroy
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function is called unconditionally and keyring_destroy() uses list_empty()
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on keyring->type_data.link - which is in a union with reject_error.
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Subsequently, the kernel tries to unlink the keyring from the keyring names
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list - which oopses like this:
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BUG: unable to handle kernel paging request at 00000000ffffff8a
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IP: [<ffffffff8126e051>] keyring_destroy+0x3d/0x88
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...
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Workqueue: events key_garbage_collector
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...
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RIP: 0010:[<ffffffff8126e051>] keyring_destroy+0x3d/0x88
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RSP: 0018:ffff88003e2f3d30 EFLAGS: 00010203
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RAX: 00000000ffffff82 RBX: ffff88003bf1a900 RCX: 0000000000000000
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RDX: 0000000000000000 RSI: 000000003bfc6901 RDI: ffffffff81a73a40
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RBP: ffff88003e2f3d38 R08: 0000000000000152 R09: 0000000000000000
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R10: ffff88003e2f3c18 R11: 000000000000865b R12: ffff88003bf1a900
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R13: 0000000000000000 R14: ffff88003bf1a908 R15: ffff88003e2f4000
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...
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CR2: 00000000ffffff8a CR3: 000000003e3ec000 CR4: 00000000000006f0
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...
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Call Trace:
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[<ffffffff8126c756>] key_gc_unused_keys.constprop.1+0x5d/0x10f
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[<ffffffff8126ca71>] key_garbage_collector+0x1fa/0x351
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[<ffffffff8105ec9b>] process_one_work+0x28e/0x547
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[<ffffffff8105fd17>] worker_thread+0x26e/0x361
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[<ffffffff8105faa9>] ? rescuer_thread+0x2a8/0x2a8
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[<ffffffff810648ad>] kthread+0xf3/0xfb
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[<ffffffff810647ba>] ? kthread_create_on_node+0x1c2/0x1c2
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[<ffffffff815f2ccf>] ret_from_fork+0x3f/0x70
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[<ffffffff810647ba>] ? kthread_create_on_node+0x1c2/0x1c2
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Note the value in RAX. This is a 32-bit representation of -ENOKEY.
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The solution is to only call ->destroy() if the key was successfully
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instantiated.
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Reported-by: Dmitry Vyukov <dvyukov@google.com>
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Signed-off-by: David Howells <dhowells@redhat.com>
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---
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security/keys/gc.c | 6 ++++--
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1 file changed, 4 insertions(+), 2 deletions(-)
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diff --git a/security/keys/gc.c b/security/keys/gc.c
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index 39eac1fd5706..addf060399e0 100644
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--- a/security/keys/gc.c
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+++ b/security/keys/gc.c
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@@ -134,8 +134,10 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
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kdebug("- %u", key->serial);
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key_check(key);
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- /* Throw away the key data */
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- if (key->type->destroy)
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+ /* Throw away the key data if the key is instantiated */
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+ if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags) &&
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+ !test_bit(KEY_FLAG_NEGATIVE, &key->flags) &&
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+ key->type->destroy)
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key->type->destroy(key);
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security_key_free(key);
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--
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2.4.3
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@ -0,0 +1,34 @@
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From 637114624bcf468a32af842a4356aab607457e62 Mon Sep 17 00:00:00 2001
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From: David Howells <dhowells@redhat.com>
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Date: Mon, 19 Oct 2015 11:33:38 +0100
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Subject: [PATCH 2/2] KEYS: Don't permit request_key() to construct a new
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keyring
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If request_key() is used to find a keyring, only do the search part - don't
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do the construction part if the keyring was not found by the search. We
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don't really want keyrings in the negative instantiated state since the
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rejected/negative instantiation error value in the payload is unioned with
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keyring metadata.
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Signed-off-by: David Howells <dhowells@redhat.com>
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---
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security/keys/request_key.c | 3 +++
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1 file changed, 3 insertions(+)
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diff --git a/security/keys/request_key.c b/security/keys/request_key.c
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index 486ef6fa393b..0d6253124278 100644
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--- a/security/keys/request_key.c
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+++ b/security/keys/request_key.c
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@@ -440,6 +440,9 @@ static struct key *construct_key_and_link(struct keyring_search_context *ctx,
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kenter("");
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+ if (ctx->index_key.type == &key_type_keyring)
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+ return ERR_PTR(-EPERM);
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+
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user = key_user_lookup(current_fsuid());
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if (!user)
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return ERR_PTR(-ENOMEM);
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--
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2.4.3
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@ -587,6 +587,10 @@ Patch508: kexec-uefi-copy-secure_boot-flag-in-boot-params.patch
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#rhbz 1239050
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Patch509: ideapad-laptop-Add-Lenovo-Yoga-3-14-to-no_hw_rfkill-.patch
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#rhbz 1272172
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Patch510: 0001-KEYS-Fix-crash-when-attempt-to-garbage-collect-an-un.patch
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Patch511: 0002-KEYS-Don-t-permit-request_key-to-construct-a-new-key.patch
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Patch904: kdbus.patch
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# END OF PATCH DEFINITIONS
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@ -2032,6 +2036,9 @@ fi
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#
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#
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%changelog
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* Mon Oct 19 2015 Josh Boyer <jwboyer@fedoraproject.org>
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- Fix crash in key garbage collector when using request_key (rhbz 1272172)
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* Fri Oct 16 2015 Laura Abbott <labbott@redhat.com> - 4.3.0-0.rc5.git2.1
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- Linux v4.3-rc5-65-g69984b6
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