Messages in this thread Patch in this message | | | From | Luis Henriques <> | Subject | [PATCH 3.11 68/93] futex-prevent-requeue-pi-on-same-futex.patch futex: Forbid uaddr == uaddr2 in futex_requeue(..., requeue_pi=1) | Date | Mon, 23 Jun 2014 14:02:47 +0100 |
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3.11.10.12 -stable review patch. If anyone has any objections, please let me know.
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From: Thomas Gleixner <tglx@linutronix.de>
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 <wad@chromium.org> Signed-off-by: Kees Cook <keescook@chromium.org> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Darren Hart <dvhart@linux.intel.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Luis Henriques <luis.henriques@canonical.com> --- kernel/futex.c | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+)
diff --git a/kernel/futex.c b/kernel/futex.c index a62447d335ab..83b44e9c26c3 100644 --- a/kernel/futex.c +++ b/kernel/futex.c @@ -1294,6 +1294,13 @@ static int futex_requeue(u32 __user *uaddr1, unsigned int flags, 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. */ @@ -1331,6 +1338,15 @@ 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); @@ -2361,6 +2377,15 @@ 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); -- 1.9.1
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