77 lines
2.2 KiB
Diff
77 lines
2.2 KiB
Diff
Date: Tue, 03 Jun 2014 12:27:06 -0000
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From: Thomas Gleixner <tglx@linutronix.de>
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Subject: [patch 1/4] futex-prevent-requeue-pi-on-same-futex.patch futex:
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Forbid uaddr == uaddr2 in futex_requeue(..., requeue_pi=1)
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If uaddr == uaddr2, then we have broken the rule of only requeueing
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from a non-pi futex to a pi futex with this call. If we attempt this,
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then dangling pointers may be left for rt_waiter resulting in an
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exploitable condition.
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This change brings futex_requeue() into line with
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futex_wait_requeue_pi() which performs the same check as per commit
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6f7b0a2a5 (futex: Forbid uaddr == uaddr2 in futex_wait_requeue_pi())
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[ tglx: Compare the resulting keys as well, as uaddrs might be
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different depending on the mapping ]
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Fixes CVE-2014-3153.
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Reported-by: Pinkie Pie
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Signed-off-by: Will Drewry <wad@chromium.org>
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Signed-off-by: Kees Cook <keescook@chromium.org>
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Cc: stable@vger.kernel.org
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Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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---
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kernel/futex.c | 25 +++++++++++++++++++++++++
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1 file changed, 25 insertions(+)
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--- a/kernel/futex.c
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+++ b/kernel/futex.c
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@@ -1428,6 +1428,13 @@ static int futex_requeue(u32 __user *uad
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if (requeue_pi) {
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/*
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+ * Requeue PI only works on two distinct uaddrs. This
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+ * check is only valid for private futexes. See below.
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+ */
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+ if (uaddr1 == uaddr2)
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+ return -EINVAL;
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+
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+ /*
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* requeue_pi requires a pi_state, try to allocate it now
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* without any locks in case it fails.
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*/
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@@ -1465,6 +1472,15 @@ retry:
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if (unlikely(ret != 0))
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goto out_put_key1;
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+ /*
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+ * The check above which compares uaddrs is not sufficient for
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+ * shared futexes. We need to compare the keys:
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+ */
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+ if (requeue_pi && match_futex(&key1, &key2)) {
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+ ret = -EINVAL;
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+ goto out_put_keys;
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+ }
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+
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hb1 = hash_futex(&key1);
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hb2 = hash_futex(&key2);
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@@ -2511,6 +2527,15 @@ static int futex_wait_requeue_pi(u32 __u
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if (ret)
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goto out_key2;
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+ /*
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+ * The check above which compares uaddrs is not sufficient for
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+ * shared futexes. We need to compare the keys:
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+ */
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+ if (match_futex(&q.key, &key2)) {
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+ ret = -EINVAL;
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+ goto out_put_keys;
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+ }
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+
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/* Queue the futex_q, drop the hb lock, wait for wakeup. */
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futex_wait_queue_me(hb, &q, to);
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