| Message ID | 20230119070004.321358-2-alxndr@bu.edu (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | memory: prevent dma-reentracy issues | expand |
Hi Alex, Generally, this looks good, but I do have a comment below... On Thursday, 2023-01-19 at 02:00:02 -05, 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-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/qdev-core.h | 7 +++++++ > softmmu/memory.c | 15 +++++++++++++++ > softmmu/trace-events | 1 + > 3 files changed, 23 insertions(+) > > diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h > index 35fddb19a6..8858195262 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 e05332d07f..90ffaaa4f5 100644 > --- a/softmmu/memory.c > +++ b/softmmu/memory.c > @@ -533,6 +533,7 @@ 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) { > @@ -542,6 +543,17 @@ 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); I don't know how likely this is to happen, but according to: - https://qemu-project.gitlab.io/qemu/devel/qom.html#c.object_dynamic_cast it is possible for the object_dynamic_cast() function to return NULL, so it might make sense to wrap the subsequent calls in a test of dev != NULL. Thanks, Darren. > + if (dev->mem_reentrancy_guard.engaged_in_io) { > + trace_memory_region_reentrant_io(get_cpu_index(), mr, addr, size); > + return MEMTX_ERROR; > + } > + dev->mem_reentrancy_guard.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); > @@ -556,6 +568,9 @@ static MemTxResult access_with_adjusted_size(hwaddr addr, > access_mask, attrs); > } > } > + if (dev) { > + dev->mem_reentrancy_guard.engaged_in_io = false; > + } > return r; > } > > diff --git a/softmmu/trace-events b/softmmu/trace-events > index 22606dc27b..62d04ea9a7 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)" > -- > 2.39.0
On Fri, 20 Jan 2023 at 14:42, Darren Kenny <darren.kenny@oracle.com> wrote: > Generally, this looks good, but I do have a comment below... > > On Thursday, 2023-01-19 at 02:00:02 -05, 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: > > diff --git a/softmmu/memory.c b/softmmu/memory.c > > index e05332d07f..90ffaaa4f5 100644 > > --- a/softmmu/memory.c > > +++ b/softmmu/memory.c > > @@ -533,6 +533,7 @@ 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) { > > @@ -542,6 +543,17 @@ 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); > > I don't know how likely this is to happen, but according to: > > - https://qemu-project.gitlab.io/qemu/devel/qom.html#c.object_dynamic_cast > > it is possible for the object_dynamic_cast() function to return NULL, > so it might make sense to wrap the subsequent calls in a test of dev != > NULL. Yes. This came up in a previous version of this: https://lore.kernel.org/qemu-devel/CAFEAcA8E4nDoAWcj-v-dED-0hDtXGjJNSp3A=kdGF8UOCw0DrQ@mail.gmail.com/ It's generally a bug to call object_dynamic_cast() and then not check the return value. thanks -- PMM
On 230120 1447, Peter Maydell wrote: > On Fri, 20 Jan 2023 at 14:42, Darren Kenny <darren.kenny@oracle.com> wrote: > > Generally, this looks good, but I do have a comment below... > > > > On Thursday, 2023-01-19 at 02:00:02 -05, 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: > > > > diff --git a/softmmu/memory.c b/softmmu/memory.c > > > index e05332d07f..90ffaaa4f5 100644 > > > --- a/softmmu/memory.c > > > +++ b/softmmu/memory.c > > > @@ -533,6 +533,7 @@ 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) { > > > @@ -542,6 +543,17 @@ 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); > > > > I don't know how likely this is to happen, but according to: > > > > - https://qemu-project.gitlab.io/qemu/devel/qom.html#c.object_dynamic_cast > > > > it is possible for the object_dynamic_cast() function to return NULL, > > so it might make sense to wrap the subsequent calls in a test of dev != > > NULL. > > Yes. This came up in a previous version of this: > https://lore.kernel.org/qemu-devel/CAFEAcA8E4nDoAWcj-v-dED-0hDtXGjJNSp3A=kdGF8UOCw0DrQ@mail.gmail.com/ > > It's generally a bug to call object_dynamic_cast() and then not check > the return value. > Sorry I missed that - Will be fixed in V5. -Alex > thanks > -- PMM
diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h index 35fddb19a6..8858195262 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 e05332d07f..90ffaaa4f5 100644 --- a/softmmu/memory.c +++ b/softmmu/memory.c @@ -533,6 +533,7 @@ 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) { @@ -542,6 +543,17 @@ 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->mem_reentrancy_guard.engaged_in_io) { + trace_memory_region_reentrant_io(get_cpu_index(), mr, addr, size); + return MEMTX_ERROR; + } + dev->mem_reentrancy_guard.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); @@ -556,6 +568,9 @@ static MemTxResult access_with_adjusted_size(hwaddr addr, access_mask, attrs); } } + if (dev) { + dev->mem_reentrancy_guard.engaged_in_io = false; + } return r; } diff --git a/softmmu/trace-events b/softmmu/trace-events index 22606dc27b..62d04ea9a7 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)"
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/qdev-core.h | 7 +++++++ softmmu/memory.c | 15 +++++++++++++++ softmmu/trace-events | 1 + 3 files changed, 23 insertions(+)