Add a flag to the DeviceState, when a device is engaged in
PIO/MMIO/DMA.
This flag is set/checked prior to calling a device's MemoryRegion
handlers, and set when device code initiates DMA. The purpose
of this
flag is to prevent two types of DMA-based reentrancy issues:
1.) mmio -> dma -> mmio case
2.) bh -> dma write -> mmio case
These issues have led to problems such as stack-exhaustion and
use-after-frees.
Summary of the problem from Peter Maydell:
https://lore.kernel.org/qemu-devel/cafeaca_23vc7he3iam-jva6w38lk4hjowae5kcknhprd5fp...@mail.gmail.com
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/62
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/540
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/541
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/556
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/557
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/827
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1282
Resolves: CVE-2023-0330
Signed-off-by: Alexander Bulekov <alx...@bu.edu>
Reviewed-by: Thomas Huth <th...@redhat.com>
---
include/exec/memory.h | 5 +++++
include/hw/qdev-core.h | 7 +++++++
softmmu/memory.c | 16 ++++++++++++++++
3 files changed, 28 insertions(+)
diff --git a/include/exec/memory.h b/include/exec/memory.h
index 15ade918ba..e45ce6061f 100644
--- a/include/exec/memory.h
+++ b/include/exec/memory.h
@@ -767,6 +767,8 @@ struct MemoryRegion {
bool is_iommu;
RAMBlock *ram_block;
Object *owner;
+ /* owner as TYPE_DEVICE. Used for re-entrancy checks in MR
access hotpath */
+ DeviceState *dev;
const MemoryRegionOps *ops;
void *opaque;
@@ -791,6 +793,9 @@ struct MemoryRegion {
unsigned ioeventfd_nb;
MemoryRegionIoeventfd *ioeventfds;
RamDiscardManager *rdm; /* Only for RAM */
+
+ /* For devices designed to perform re-entrant IO into their
own IO MRs */
+ bool disable_reentrancy_guard;
};
struct IOMMUMemoryRegion {
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index bd50ad5ee1..7623703943 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -162,6 +162,10 @@ struct NamedClockList {
QLIST_ENTRY(NamedClockList) node;
};
+typedef struct {
+ bool engaged_in_io;
+} MemReentrancyGuard;
+
/**
* DeviceState:
* @realized: Indicates whether the device has been fully
constructed.
@@ -194,6 +198,9 @@ struct DeviceState {
int alias_required_for_version;
ResettableState reset;
GSList *unplug_blockers;
+
+ /* Is the device currently in mmio/pio/dma? Used to prevent
re-entrancy */
+ MemReentrancyGuard mem_reentrancy_guard;
};
struct DeviceListener {
diff --git a/softmmu/memory.c b/softmmu/memory.c
index b1a6cae6f5..fe23f0e5ce 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -542,6 +542,18 @@ static MemTxResult
access_with_adjusted_size(hwaddr addr,
access_size_max = 4;
}
+ /* Do not allow more than one simultaneous access to a
device's IO Regions */
+ if (mr->dev && !mr->disable_reentrancy_guard &&
+ !mr->ram_device && !mr->ram && !mr->rom_device &&
!mr->readonly) {
+ if (mr->dev->mem_reentrancy_guard.engaged_in_io) {
+ warn_report("Blocked re-entrant IO on "
+ "MemoryRegion: %s at addr: 0x%" HWADDR_PRIX,
+ memory_region_name(mr), addr);
+ return MEMTX_ACCESS_ERROR;
