On 230428 1015, Thomas Huth wrote: > On 28/04/2023 10.12, Daniel P. Berrangé wrote: > > On Thu, Apr 27, 2023 at 05:10:06PM -0400, 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 > > > 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; > > > > If we issue this warn_report on every invalid memory access, is this > > going to become a denial of service by flooding logs, or is the > > return MEMTX_ACCESS_ERROR, sufficient to ensure this is only printed > > *once* in the lifetime of the QEMU process ? > > Maybe it's better to use warn_report_once() here instead?
Sounds good - should I respin the series to change this? -Alex