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From 05fd13592b60c3e9873f56705f80ff934e98b046 Mon Sep 17 00:00:00 2001
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From: David Howells <dhowells@redhat.com>
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Date: Mon, 18 Jan 2016 10:53:31 +0000
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Subject: [PATCH] KEYS: Fix keyring ref leak in join_session_keyring()
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This fixes CVE-2016-0728.
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If a thread is asked to join as a session keyring the keyring that's already
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set as its session, we leak a keyring reference.
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This can be tested with the following program:
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#include <stddef.h>
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#include <stdio.h>
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#include <sys/types.h>
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#include <keyutils.h>
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int main(int argc, const char *argv[])
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{
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int i = 0;
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key_serial_t serial;
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serial = keyctl(KEYCTL_JOIN_SESSION_KEYRING,
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"leaked-keyring");
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if (serial < 0) {
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perror("keyctl");
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return -1;
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}
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if (keyctl(KEYCTL_SETPERM, serial,
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KEY_POS_ALL | KEY_USR_ALL) < 0) {
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perror("keyctl");
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return -1;
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}
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for (i = 0; i < 100; i++) {
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serial = keyctl(KEYCTL_JOIN_SESSION_KEYRING,
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"leaked-keyring");
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if (serial < 0) {
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perror("keyctl");
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return -1;
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}
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}
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return 0;
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}
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If, after the program has run, there something like the following line in
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/proc/keys:
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3f3d898f I--Q--- 100 perm 3f3f0000 0 0 keyring leaked-keyring: empty
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with a usage count of 100 * the number of times the program has been run,
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then the kernel is malfunctioning. If leaked-keyring has zero usages or
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has been garbage collected, then the problem is fixed.
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Reported-by: Yevgeny Pats <yevgeny@perception-point.io>
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Signed-off-by: David Howells <dhowells@redhat.com>
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RH-bugzilla: 1298036
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---
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security/keys/process_keys.c | 1 +
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1 file changed, 1 insertion(+)
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diff --git a/security/keys/process_keys.c b/security/keys/process_keys.c
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index 43b4cddbf2b3..7877e5cd4e23 100644
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--- a/security/keys/process_keys.c
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+++ b/security/keys/process_keys.c
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@@ -794,6 +794,7 @@ long join_session_keyring(const char *name)
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ret = PTR_ERR(keyring);
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goto error2;
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} else if (keyring == new->session_keyring) {
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+ key_put(keyring);
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ret = 0;
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goto error2;
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}
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--
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2.5.0
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