81 lines
2.9 KiB
Diff
81 lines
2.9 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Akihiko Odaki <akihiko.odaki@daynix.com>
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Date: Tue, 31 Jan 2023 12:00:37 +0900
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Subject: [PATCH] hw/timer/hpet: Fix expiration time overflow
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The expiration time provided for timer_mod() can overflow if a
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ridiculously large value is set to the comparator register. The
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resulting value can represent a past time after rounded, forcing the
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timer to fire immediately. If the timer is configured as periodic, it
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will rearm the timer again, and form an endless loop.
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Check if the expiration value will overflow, and if it will, stop the
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timer instead of rearming the timer with the overflowed time.
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This bug was found by Alexander Bulekov when fuzzing igb, a new
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network device emulation:
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https://patchew.org/QEMU/20230129053316.1071513-1-alxndr@bu.edu/
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The fixed test case is:
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fuzz/crash_2d7036941dcda1ad4380bb8a9174ed0c949bcefd
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Fixes: 16b29ae180 ("Add HPET emulation to qemu (Beth Kon)")
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Signed-off-by: Akihiko Odaki <akihiko.odaki@daynix.com>
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Acked-by: Michael S. Tsirkin <mst@redhat.com>
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Message-Id: <20230131030037.18856-1-akihiko.odaki@daynix.com>
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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(cherry-picked from commit 37d2bcbc2a4e9c2e9061bec72a32c7e49b9f81ec)
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Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
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---
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hw/timer/hpet.c | 19 +++++++++++++------
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1 file changed, 13 insertions(+), 6 deletions(-)
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diff --git a/hw/timer/hpet.c b/hw/timer/hpet.c
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index 9520471be2..5f88ffdef8 100644
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--- a/hw/timer/hpet.c
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+++ b/hw/timer/hpet.c
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@@ -352,6 +352,16 @@ static const VMStateDescription vmstate_hpet = {
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}
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};
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+static void hpet_arm(HPETTimer *t, uint64_t ticks)
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+{
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+ if (ticks < ns_to_ticks(INT64_MAX / 2)) {
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+ timer_mod(t->qemu_timer,
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+ qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + ticks_to_ns(ticks));
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+ } else {
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+ timer_del(t->qemu_timer);
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+ }
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+}
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+
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/*
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* timer expiration callback
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*/
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@@ -374,13 +384,11 @@ static void hpet_timer(void *opaque)
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}
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}
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diff = hpet_calculate_diff(t, cur_tick);
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- timer_mod(t->qemu_timer,
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- qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + (int64_t)ticks_to_ns(diff));
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+ hpet_arm(t, diff);
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} else if (t->config & HPET_TN_32BIT && !timer_is_periodic(t)) {
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if (t->wrap_flag) {
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diff = hpet_calculate_diff(t, cur_tick);
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- timer_mod(t->qemu_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) +
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- (int64_t)ticks_to_ns(diff));
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+ hpet_arm(t, diff);
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t->wrap_flag = 0;
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}
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}
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@@ -407,8 +415,7 @@ static void hpet_set_timer(HPETTimer *t)
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t->wrap_flag = 1;
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}
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}
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- timer_mod(t->qemu_timer,
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- qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL) + (int64_t)ticks_to_ns(diff));
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+ hpet_arm(t, diff);
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}
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static void hpet_del_timer(HPETTimer *t)
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