[linux] 02/03: KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring

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carnil pushed a commit to branch sid
in repository linux.

commit a4b71a2ac3bfac58dbc6d411abdb414d32dd2efe
Author: Salvatore Bonaccorso <carnil at debian.org>
Date:   Mon Oct 19 21:31:55 2015 +0200

    KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring
---
 debian/changelog                                   |  1 +
 ...ash-when-attempt-to-garbage-collect-an-un.patch | 77 ++++++++++++++++++++++
 debian/patches/series                              |  1 +
 3 files changed, 79 insertions(+)

diff --git a/debian/changelog b/debian/changelog
index 689cc99..1475550 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,6 +1,7 @@
 linux (4.2.3-3) UNRELEASED; urgency=medium
 
   * KEYS: Fix race between key destruction and finding a keyring by name
+  * KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring
 
  -- Salvatore Bonaccorso <carnil at debian.org>  Mon, 19 Oct 2015 21:23:18 +0200
 
diff --git a/debian/patches/bugfix/all/0001-KEYS-Fix-crash-when-attempt-to-garbage-collect-an-un.patch b/debian/patches/bugfix/all/0001-KEYS-Fix-crash-when-attempt-to-garbage-collect-an-un.patch
new file mode 100644
index 0000000..d2850c9
--- /dev/null
+++ b/debian/patches/bugfix/all/0001-KEYS-Fix-crash-when-attempt-to-garbage-collect-an-un.patch
@@ -0,0 +1,77 @@
+From: David Howells <dhowells at redhat.com>
+Date: Thu, 15 Oct 2015 17:21:37 +0100
+Subject: KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring
+Origin: http://pkgs.fedoraproject.org/cgit/kernel.git/plain/0001-KEYS-Fix-crash-when-attempt-to-garbage-collect-an-un.patch?id=d76d5fe34b5c151ad83761160998b1075729b541
+
+    The following sequence of commands:
+
+        i=`keyctl add user a a @s`
+        keyctl request2 keyring foo bar @t
+        keyctl unlink $i @s
+
+    tries to invoke an upcall to instantiate a keyring if one doesn't already
+    exist by that name within the user's keyring set.  However, if the upcall
+    fails, the code sets keyring->type_data.reject_error to -ENOKEY or some
+    other error code.  When the key is garbage collected, the key destroy
+    function is called unconditionally and keyring_destroy() uses list_empty()
+    on keyring->type_data.link - which is in a union with reject_error.
+    Subsequently, the kernel tries to unlink the keyring from the keyring names
+    list - which oopses like this:
+
+    	BUG: unable to handle kernel paging request at 00000000ffffff8a
+    	IP: [<ffffffff8126e051>] keyring_destroy+0x3d/0x88
+    	...
+    	Workqueue: events key_garbage_collector
+    	...
+    	RIP: 0010:[<ffffffff8126e051>] keyring_destroy+0x3d/0x88
+    	RSP: 0018:ffff88003e2f3d30  EFLAGS: 00010203
+    	RAX: 00000000ffffff82 RBX: ffff88003bf1a900 RCX: 0000000000000000
+    	RDX: 0000000000000000 RSI: 000000003bfc6901 RDI: ffffffff81a73a40
+    	RBP: ffff88003e2f3d38 R08: 0000000000000152 R09: 0000000000000000
+    	R10: ffff88003e2f3c18 R11: 000000000000865b R12: ffff88003bf1a900
+    	R13: 0000000000000000 R14: ffff88003bf1a908 R15: ffff88003e2f4000
+    	...
+    	CR2: 00000000ffffff8a CR3: 000000003e3ec000 CR4: 00000000000006f0
+    	...
+    	Call Trace:
+    	 [<ffffffff8126c756>] key_gc_unused_keys.constprop.1+0x5d/0x10f
+    	 [<ffffffff8126ca71>] key_garbage_collector+0x1fa/0x351
+    	 [<ffffffff8105ec9b>] process_one_work+0x28e/0x547
+    	 [<ffffffff8105fd17>] worker_thread+0x26e/0x361
+    	 [<ffffffff8105faa9>] ? rescuer_thread+0x2a8/0x2a8
+    	 [<ffffffff810648ad>] kthread+0xf3/0xfb
+    	 [<ffffffff810647ba>] ? kthread_create_on_node+0x1c2/0x1c2
+    	 [<ffffffff815f2ccf>] ret_from_fork+0x3f/0x70
+    	 [<ffffffff810647ba>] ? kthread_create_on_node+0x1c2/0x1c2
+
+    Note the value in RAX.  This is a 32-bit representation of -ENOKEY.
+
+    The solution is to only call ->destroy() if the key was successfully
+    instantiated.
+
+    Reported-by: Dmitry Vyukov <dvyukov at google.com>
+    Signed-off-by: David Howells <dhowells at redhat.com>
+---
+ security/keys/gc.c | 6 ++++--
+ 1 file changed, 4 insertions(+), 2 deletions(-)
+
+diff --git a/security/keys/gc.c b/security/keys/gc.c
+index 39eac1fd5706..addf060399e0 100644
+--- a/security/keys/gc.c
++++ b/security/keys/gc.c
+@@ -134,8 +134,10 @@ static noinline void key_gc_unused_keys(struct list_head *keys)
+ 		kdebug("- %u", key->serial);
+ 		key_check(key);
+ 
+-		/* Throw away the key data */
+-		if (key->type->destroy)
++		/* Throw away the key data if the key is instantiated */
++		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags) &&
++		    !test_bit(KEY_FLAG_NEGATIVE, &key->flags) &&
++		    key->type->destroy)
+ 			key->type->destroy(key);
+ 
+ 		security_key_free(key);
+-- 
+2.4.3
+
diff --git a/debian/patches/series b/debian/patches/series
index 46ea6db..67f0b4e 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -109,3 +109,4 @@ bugfix/all/nbd-remove-variable-pid.patch
 bugfix/all/nbd-add-locking-for-tasks.patch
 
 bugfix/all/0001-KEYS-Fix-race-between-key-destruction-and-finding-a-.patch
+bugfix/all/0001-KEYS-Fix-crash-when-attempt-to-garbage-collect-an-un.patch

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