From: David Howells <dhowells@redhat.com>

Date: Fri, 10 Sep 2010 08:59:51 +0000 (+0100)

Subject: KEYS: Fix bug in keyctl_session_to_parent() if parent has no session keyring

X-Git-Url: http://git.kernel.org/?p=linux%2Fkernel%2Fgit%2Ftorvalds%2Flinux-2.6.git;a=commitdiff_plain;h=3d96406c7da1ed5811ea52a3b0905f4f0e295376

KEYS: Fix bug in keyctl_session_to_parent() if parent has no session keyring

Fix a bug in keyctl_session_to_parent() whereby it tries to check the ownership

of the parent process's session keyring whether or not the parent has a session

keyring [CVE-2010-2960].

This results in the following oops:

  BUG: unable to handle kernel NULL pointer dereference at 00000000000000a0

  IP: [<ffffffff811ae4dd>] keyctl_session_to_parent+0x251/0x443

  ...

  Call Trace:

   [<ffffffff811ae2f3>] ? keyctl_session_to_parent+0x67/0x443

   [<ffffffff8109d286>] ? __do_fault+0x24b/0x3d0

   [<ffffffff811af98c>] sys_keyctl+0xb4/0xb8

   [<ffffffff81001eab>] system_call_fastpath+0x16/0x1b

if the parent process has no session keyring.

If the system is using pam_keyinit then it mostly protected against this as all

processes derived from a login will have inherited the session keyring created

by pam_keyinit during the log in procedure.

To test this, pam_keyinit calls need to be commented out in /etc/pam.d/.

Reported-by: Tavis Ormandy <taviso@cmpxchg8b.com>

Signed-off-by: David Howells <dhowells@redhat.com>

Acked-by: Tavis Ormandy <taviso@cmpxchg8b.com>

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

---

[ 2.6.32 backport ]

diff a/security/keys/keyctl.c b/security/keys/keyctl.c

--- a/security/keys/keyctl.c

+++ b/security/keys/keyctl.c

@@ -1291,7 +1291,8 @@ long keyctl_session_to_parent(void)

 		goto not_permitted;

 	/* the keyrings must have the same UID */

-	if (pcred ->tgcred->session_keyring->uid != mycred->euid ||

+	if ((pcred->tgcred->session_keyring &&

+	     pcred->tgcred->session_keyring->uid != mycred->euid) ||

 	    mycred->tgcred->session_keyring->uid != mycred->euid)

 		goto not_permitted;