From e0c811c2d13f995fe1b095f48637316be5978b0e Mon Sep 17 00:00:00 2001 From: Jon Maloy Date: Tue, 9 May 2023 10:29:03 -0400 Subject: [PATCH 01/15] memory: prevent dma-reentracy issues RH-Author: Jon Maloy RH-MergeRequest: 277: memory: prevent dma-reentracy issues RH-Bugzilla: 1999236 RH-Acked-by: Thomas Huth RH-Acked-by: Miroslav Rezanina RH-Commit: [1/12] 8fced41b4b2105343e8f0250286b771bcb43c81f (redhat/rhel/src/qemu-kvm/jons-qemu-kvm-2) Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1999236 Upstream: Merged CVE: CVE-2021-3750 CVE: CVE-2023-0330 commit a2e1753b8054344f32cf94f31c6399a58794a380 Author: Alexander Bulekov Date: Thu Apr 27 17:10:06 2023 -0400 memory: prevent dma-reentracy issues 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 Resolves: https://gitlab.com/qemu-project/qemu/-/issues/1282 Resolves: CVE-2023-0330 Signed-off-by: Alexander Bulekov Reviewed-by: Thomas Huth Message-Id: <20230427211013.2994127-2-alxndr@bu.edu> [thuth: Replace warn_report() with warn_report_once()] Signed-off-by: Thomas Huth Signed-off-by: Jon Maloy --- 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 20f1b27377..e089f90f9b 100644 --- a/include/exec/memory.h +++ b/include/exec/memory.h @@ -734,6 +734,8 @@ 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; @@ -757,6 +759,9 @@ 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 20d3066595..14226f860d 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. @@ -193,6 +197,9 @@ 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 */ + MemReentrancyGuard mem_reentrancy_guard; }; struct DeviceListener { diff --git a/softmmu/memory.c b/softmmu/memory.c index 7340e19ff5..102f0a4248 100644 --- a/softmmu/memory.c +++ b/softmmu/memory.c @@ -541,6 +541,18 @@ 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_once("Blocked re-entrant IO on MemoryRegion: " + "%s at addr: 0x%" HWADDR_PRIX, + memory_region_name(mr), addr); + return MEMTX_ACCESS_ERROR; + } + mr->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); @@ -555,6 +567,9 @@ static MemTxResult access_with_adjusted_size(hwaddr addr, access_mask, attrs); } } + if (mr->dev) { + mr->dev->mem_reentrancy_guard.engaged_in_io = false; + } return r; } @@ -1169,6 +1184,7 @@ static void memory_region_do_init(MemoryRegion *mr, } mr->name = g_strdup(name); mr->owner = owner; + mr->dev = (DeviceState *) object_dynamic_cast(mr->owner, TYPE_DEVICE); mr->ram_block = NULL; if (name) { -- 2.37.3