a39364b9d1
The previous version was picked from the mailing list and still had an object_dynamic_cast call in a hot path, which is avoided with the version that landed in git. Also adds a few more exceptions for devices that need reentrancy. Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
131 lines
4.6 KiB
Diff
131 lines
4.6 KiB
Diff
From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
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From: Alexander Bulekov <alxndr@bu.edu>
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Date: Thu, 27 Apr 2023 17:10:06 -0400
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Subject: [PATCH] memory: prevent dma-reentracy issues
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Add a flag to the DeviceState, when a device is engaged in PIO/MMIO/DMA.
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This flag is set/checked prior to calling a device's MemoryRegion
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handlers, and set when device code initiates DMA. The purpose of this
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flag is to prevent two types of DMA-based reentrancy issues:
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1.) mmio -> dma -> mmio case
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2.) bh -> dma write -> mmio case
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These issues have led to problems such as stack-exhaustion and
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use-after-frees.
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Summary of the problem from Peter Maydell:
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https://lore.kernel.org/qemu-devel/CAFEAcA_23vc7hE3iaM-JVA6W38LK4hJoWae5KcknhPRD5fPBZA@mail.gmail.com
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Resolves: https://gitlab.com/qemu-project/qemu/-/issues/62
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Resolves: https://gitlab.com/qemu-project/qemu/-/issues/540
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Resolves: https://gitlab.com/qemu-project/qemu/-/issues/541
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Resolves: https://gitlab.com/qemu-project/qemu/-/issues/556
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Resolves: https://gitlab.com/qemu-project/qemu/-/issues/557
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Resolves: https://gitlab.com/qemu-project/qemu/-/issues/827
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Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1282
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Resolves: CVE-2023-0330
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Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
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Reviewed-by: Thomas Huth <thuth@redhat.com>
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Message-Id: <20230427211013.2994127-2-alxndr@bu.edu>
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[thuth: Replace warn_report() with warn_report_once()]
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Signed-off-by: Thomas Huth <thuth@redhat.com>
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(cherry-picked from commit a2e1753b8054344f32cf94f31c6399a58794a380)
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Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
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---
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include/exec/memory.h | 5 +++++
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include/hw/qdev-core.h | 7 +++++++
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softmmu/memory.c | 16 ++++++++++++++++
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3 files changed, 28 insertions(+)
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diff --git a/include/exec/memory.h b/include/exec/memory.h
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index 15ade918ba..e45ce6061f 100644
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--- a/include/exec/memory.h
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+++ b/include/exec/memory.h
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@@ -767,6 +767,8 @@ struct MemoryRegion {
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bool is_iommu;
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RAMBlock *ram_block;
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Object *owner;
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+ /* owner as TYPE_DEVICE. Used for re-entrancy checks in MR access hotpath */
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+ DeviceState *dev;
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const MemoryRegionOps *ops;
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void *opaque;
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@@ -791,6 +793,9 @@ struct MemoryRegion {
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unsigned ioeventfd_nb;
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MemoryRegionIoeventfd *ioeventfds;
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RamDiscardManager *rdm; /* Only for RAM */
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+
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+ /* For devices designed to perform re-entrant IO into their own IO MRs */
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+ bool disable_reentrancy_guard;
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};
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struct IOMMUMemoryRegion {
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diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
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index bd50ad5ee1..7623703943 100644
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--- a/include/hw/qdev-core.h
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+++ b/include/hw/qdev-core.h
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@@ -162,6 +162,10 @@ struct NamedClockList {
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QLIST_ENTRY(NamedClockList) node;
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};
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+typedef struct {
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+ bool engaged_in_io;
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+} MemReentrancyGuard;
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+
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/**
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* DeviceState:
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* @realized: Indicates whether the device has been fully constructed.
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@@ -194,6 +198,9 @@ struct DeviceState {
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int alias_required_for_version;
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ResettableState reset;
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GSList *unplug_blockers;
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+
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+ /* Is the device currently in mmio/pio/dma? Used to prevent re-entrancy */
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+ MemReentrancyGuard mem_reentrancy_guard;
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};
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struct DeviceListener {
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diff --git a/softmmu/memory.c b/softmmu/memory.c
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index b1a6cae6f5..b7b3386e9d 100644
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--- a/softmmu/memory.c
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+++ b/softmmu/memory.c
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@@ -542,6 +542,18 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
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access_size_max = 4;
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}
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+ /* Do not allow more than one simultaneous access to a device's IO Regions */
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+ if (mr->dev && !mr->disable_reentrancy_guard &&
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+ !mr->ram_device && !mr->ram && !mr->rom_device && !mr->readonly) {
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+ if (mr->dev->mem_reentrancy_guard.engaged_in_io) {
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+ warn_report_once("Blocked re-entrant IO on MemoryRegion: "
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+ "%s at addr: 0x%" HWADDR_PRIX,
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+ memory_region_name(mr), addr);
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+ return MEMTX_ACCESS_ERROR;
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+ }
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+ mr->dev->mem_reentrancy_guard.engaged_in_io = true;
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+ }
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+
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/* FIXME: support unaligned access? */
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access_size = MAX(MIN(size, access_size_max), access_size_min);
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access_mask = MAKE_64BIT_MASK(0, access_size * 8);
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@@ -556,6 +568,9 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
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access_mask, attrs);
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}
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}
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+ if (mr->dev) {
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+ mr->dev->mem_reentrancy_guard.engaged_in_io = false;
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+ }
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return r;
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}
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@@ -1170,6 +1185,7 @@ static void memory_region_do_init(MemoryRegion *mr,
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}
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mr->name = g_strdup(name);
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mr->owner = owner;
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+ mr->dev = (DeviceState *) object_dynamic_cast(mr->owner, TYPE_DEVICE);
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mr->ram_block = NULL;
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if (name) {
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