[linux] 02/03: KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring (CVE-2015-7872)
debian-kernel at lists.debian.org
debian-kernel at lists.debian.org
Wed Oct 21 04:29:41 UTC 2015
This is an automated email from the git hooks/post-receive script.
carnil pushed a commit to branch jessie-security
in repository linux.
commit 30ffbd3ddc9ee5156921ae0a3a71c6c35655a68a
Author: Salvatore Bonaccorso <carnil at debian.org>
Date: Tue Oct 20 19:18:30 2015 +0200
KEYS: Fix crash when attempt to garbage collect an uninstantiated keyring (CVE-2015-7872)
---
debian/changelog | 2 +
...ash-when-attempt-to-garbage-collect-an-un.patch | 79 ++++++++++++++++++++++
debian/patches/series | 1 +
3 files changed, 82 insertions(+)
diff --git a/debian/changelog b/debian/changelog
index 921eb5f..4213f63 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -1,6 +1,8 @@
linux (3.16.7-ckt11-1+deb8u6) 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
+ (CVE-2015-7872)
-- Salvatore Bonaccorso <carnil at debian.org> Tue, 20 Oct 2015 19:12:50 +0200
diff --git a/debian/patches/bugfix/all/KEYS-Fix-crash-when-attempt-to-garbage-collect-an-un.patch b/debian/patches/bugfix/all/KEYS-Fix-crash-when-attempt-to-garbage-collect-an-un.patch
new file mode 100644
index 0000000..4369a05
--- /dev/null
+++ b/debian/patches/bugfix/all/KEYS-Fix-crash-when-attempt-to-garbage-collect-an-un.patch
@@ -0,0 +1,79 @@
+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: https://git.kernel.org/linus/f05819df10d7b09f6d1eb6f8534a8f68e5a4fe61
+
+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>
+Tested-by: Dmitry Vyukov <dvyukov at google.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 39eac1f..addf060 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);
+--
+2.6.1
+
diff --git a/debian/patches/series b/debian/patches/series
index 4565283..43076b3 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -653,3 +653,4 @@ bugfix/all/sctp-fix-race-on-protocol-netns-initialization.patch
bugfix/all/ipc-sem.c-fully-initialize-sem_array-before-making-i.patch
bugfix/all/Initialize-msg-shm-IPC-objects-before-doing-ipc_addid.patch
bugfix/all/KEYS-Fix-race-between-key-destruction-and-finding-a-.patch
+bugfix/all/KEYS-Fix-crash-when-attempt-to-garbage-collect-an-un.patch
--
Alioth's /usr/local/bin/git-commit-notice on /srv/git.debian.org/git/kernel/linux.git
More information about the Kernel-svn-changes
mailing list