From 4cca4db7bd5fb663660da34a3514d9fa8f5f14f3 Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Tue, 3 Jun 2014 12:27:06 +0000 Subject: futex-prevent-requeue-pi-on-same-futex.patch futex: Forbid uaddr == uaddr2 in futex_requeue(..., requeue_pi=1) commit e9c243a5a6de0be8e584c604d353412584b592f8 upstream. If uaddr == uaddr2, then we have broken the rule of only requeueing from a non-pi futex to a pi futex with this call. If we attempt this, then dangling pointers may be left for rt_waiter resulting in an exploitable condition. This change brings futex_requeue() in line with futex_wait_requeue_pi() which performs the same check as per commit 6f7b0a2a5c0f ("futex: Forbid uaddr == uaddr2 in futex_wait_requeue_pi()") [ tglx: Compare the resulting keys as well, as uaddrs might be different depending on the mapping ] Fixes CVE-2014-3153. Reported-by: Pinkie Pie Signed-off-by: Will Drewry Signed-off-by: Kees Cook Signed-off-by: Thomas Gleixner Reviewed-by: Darren Hart Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- kernel/futex.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) (limited to 'kernel') diff --git a/kernel/futex.c b/kernel/futex.c index ef88446c5703..c8450549f748 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1288,6 +1288,13 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags, struct futex_q *this, *next; if (requeue_pi) { + /* + * Requeue PI only works on two distinct uaddrs. This + * check is only valid for private futexes. See below. + */ + if (uaddr1 == uaddr2) + return -EINVAL; + /* * requeue_pi requires a pi_state, try to allocate it now * without any locks in case it fails. @@ -1326,6 +1333,15 @@ retry: if (unlikely(ret != 0)) goto out_put_key1; + /* + * The check above which compares uaddrs is not sufficient for + * shared futexes. We need to compare the keys: + */ + if (requeue_pi && match_futex(&key1, &key2)) { + ret = -EINVAL; + goto out_put_keys; + } + hb1 = hash_futex(&key1); hb2 = hash_futex(&key2); @@ -2357,6 +2373,15 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags, if (ret) goto out_key2; + /* + * The check above which compares uaddrs is not sufficient for + * shared futexes. We need to compare the keys: + */ + if (match_futex(&q.key, &key2)) { + ret = -EINVAL; + goto out_put_keys; + } + /* Queue the futex_q, drop the hb lock, wait for wakeup. */ futex_wait_queue_me(hb, &q, to); -- cgit v1.2.3