From: Eric Biggers <ebiggers@google.com>
Date: Tue, 18 Apr 2017 14:31:09 +0000 (+0100)
Subject: KEYS: fix keyctl_set_reqkey_keyring() to not leak thread keyrings
X-Git-Tag: v3.2.89~20
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0ebd7208190d2f7b16fee3cea05665e212cebaab;p=pandora-kernel.git

KEYS: fix keyctl_set_reqkey_keyring() to not leak thread keyrings

commit c9f838d104fed6f2f61d68164712e3204bf5271b upstream.

This fixes CVE-2017-7472.

Running the following program as an unprivileged user exhausts kernel
memory by leaking thread keyrings:

	#include <keyutils.h>

	int main()
	{
		for (;;)
			keyctl_set_reqkey_keyring(KEY_REQKEY_DEFL_THREAD_KEYRING);
	}

Fix it by only creating a new thread keyring if there wasn't one before.
To make things more consistent, make install_thread_keyring_to_cred()
and install_process_keyring_to_cred() both return 0 if the corresponding
keyring is already present.

Fixes: d84f4f992cbd ("CRED: Inaugurate COW credentials")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: David Howells <dhowells@redhat.com>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---

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