On 220609 0958, Alexander Bulekov wrote: > 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 > Signed-off-by: Alexander Bulekov <alx...@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 >
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