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[PATCH v2] memory: prevent dma-reentracy issues
From: |
Alexander Bulekov |
Subject: |
[PATCH v2] memory: prevent dma-reentracy issues |
Date: |
Thu, 9 Jun 2022 09:58:51 -0400 |
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-JVA6W38LK4hJoWae5KcknhPRD5fPBZA@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
Signed-off-by: Alexander Bulekov <alxndr@bu.edu>
---
include/hw/pci/pci.h | 13 +++++++++++--
include/hw/qdev-core.h | 3 +++
softmmu/dma-helpers.c | 12 ++++++++++++
softmmu/memory.c | 15 +++++++++++++++
softmmu/trace-events | 1 +
5 files changed, 42 insertions(+), 2 deletions(-)
diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h
index 44dacfa224..ab1ad0f7a8 100644
--- a/include/hw/pci/pci.h
+++ b/include/hw/pci/pci.h
@@ -834,8 +834,17 @@ static inline MemTxResult pci_dma_rw(PCIDevice *dev,
dma_addr_t addr,
void *buf, dma_addr_t len,
DMADirection dir, MemTxAttrs attrs)
{
- return dma_memory_rw(pci_get_address_space(dev), addr, buf, len,
- dir, attrs);
+ bool prior_engaged_state;
+ MemTxResult result;
+
+ prior_engaged_state = dev->qdev.engaged_in_io;
+
+ dev->qdev.engaged_in_io = true;
+ result = dma_memory_rw(pci_get_address_space(dev), addr, buf, len,
+ dir, attrs);
+ dev->qdev.engaged_in_io = prior_engaged_state;
+
+ return result;
}
/**
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
index 92c3d65208..6474dc51fa 100644
--- a/include/hw/qdev-core.h
+++ b/include/hw/qdev-core.h
@@ -193,6 +193,9 @@ struct DeviceState {
int instance_id_alias;
int alias_required_for_version;
ResettableState reset;
+
+ /* Is the device currently in mmio/pio/dma? Used to prevent re-entrancy */
+ int engaged_in_io;
};
struct DeviceListener {
diff --git a/softmmu/dma-helpers.c b/softmmu/dma-helpers.c
index 7820fec54c..7a4f1fb9b3 100644
--- a/softmmu/dma-helpers.c
+++ b/softmmu/dma-helpers.c
@@ -288,8 +288,16 @@ static MemTxResult dma_buf_rw(void *buf, dma_addr_t len,
dma_addr_t *residual,
uint8_t *ptr = buf;
dma_addr_t xresidual;
int sg_cur_index;
+ DeviceState *dev;
+ bool prior_engaged_state;
MemTxResult res = MEMTX_OK;
+ dev = sg->dev;
+ if (dev) {
+ prior_engaged_state = dev->engaged_in_io;
+ dev->engaged_in_io = true;
+ }
+
xresidual = sg->size;
sg_cur_index = 0;
len = MIN(len, xresidual);
@@ -302,6 +310,10 @@ static MemTxResult dma_buf_rw(void *buf, dma_addr_t len,
dma_addr_t *residual,
xresidual -= xfer;
}
+ if (dev) {
+ dev->engaged_in_io = prior_engaged_state;
+ }
+
if (residual) {
*residual = xresidual;
}
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 7ba2048836..44a14bb4f5 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -532,6 +532,7 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
uint64_t access_mask;
unsigned access_size;
unsigned i;
+ DeviceState *dev = NULL;
MemTxResult r = MEMTX_OK;
if (!access_size_min) {
@@ -541,6 +542,17 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
access_size_max = 4;
}
+ /* Do not allow more than one simultanous access to a device's IO Regions
*/
+ if (mr->owner &&
+ !mr->ram_device && !mr->ram && !mr->rom_device && !mr->readonly) {
+ dev = (DeviceState *) object_dynamic_cast(mr->owner, TYPE_DEVICE);
+ if (dev->engaged_in_io) {
+ trace_memory_region_reentrant_io(get_cpu_index(), mr, addr, size);
+ return MEMTX_ERROR;
+ }
+ dev->engaged_in_io = true;
+ }
+
/* FIXME: support unaligned access? */
access_size = MAX(MIN(size, access_size_max), access_size_min);
access_mask = MAKE_64BIT_MASK(0, access_size * 8);
@@ -555,6 +567,9 @@ static MemTxResult access_with_adjusted_size(hwaddr addr,
access_mask, attrs);
}
}
+ if (dev) {
+ dev->engaged_in_io = false;
+ }
return r;
}
diff --git a/softmmu/trace-events b/softmmu/trace-events
index 9c88887b3c..d7228316db 100644
--- a/softmmu/trace-events
+++ b/softmmu/trace-events
@@ -13,6 +13,7 @@ memory_region_ops_read(int cpu_index, void *mr, uint64_t
addr, uint64_t value, u
memory_region_ops_write(int cpu_index, void *mr, uint64_t addr, uint64_t
value, unsigned size, const char *name) "cpu %d mr %p addr 0x%"PRIx64" value
0x%"PRIx64" size %u name '%s'"
memory_region_subpage_read(int cpu_index, void *mr, uint64_t offset, uint64_t
value, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" value 0x%"PRIx64" size
%u"
memory_region_subpage_write(int cpu_index, void *mr, uint64_t offset, uint64_t
value, unsigned size) "cpu %d mr %p offset 0x%"PRIx64" value 0x%"PRIx64" size
%u"
+memory_region_reentrant_io(int cpu_index, void *mr, uint64_t offset, unsigned
size) "cpu %d mr %p offset 0x%"PRIx64" size %u"
memory_region_ram_device_read(int cpu_index, void *mr, uint64_t addr, uint64_t
value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64" size %u"
memory_region_ram_device_write(int cpu_index, void *mr, uint64_t addr,
uint64_t value, unsigned size) "cpu %d mr %p addr 0x%"PRIx64" value 0x%"PRIx64"
size %u"
memory_region_sync_dirty(const char *mr, const char *listener, int global) "mr
'%s' listener '%s' synced (global=%d)"
--
2.33.0
- [PATCH v2] memory: prevent dma-reentracy issues,
Alexander Bulekov <=