Searching for an unused bounce buffer in mReservedMemBitmap and reserving the buffer by flipping the bit is a critical section which must not be interrupted. Raise the TPL level to ensure that.
Without this fix it can happen that IoMmuDxe hands out the same bounce buffer twice, causing trouble down the road. Seen happening in practice with VirtioNetDxe setting up the network interface (and calling into IoMmuDxe from a polling timer callback) in parallel with Boot Manager doing some disk I/O. An ASSERT() in VirtioNet caught the buffer inconsistency. Full story with lots of details and discussions is available here: https://bugzilla.redhat.com/show_bug.cgi?id=2211060 v2: - add locking to IoMmuFreeBounceBuffer too, clearing bits in mReservedMemBitmap is not guaranteed to be atomic (Michael Brown). Signed-off-by: Gerd Hoffmann <kra...@redhat.com> --- OvmfPkg/IoMmuDxe/IoMmuBuffer.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/OvmfPkg/IoMmuDxe/IoMmuBuffer.c b/OvmfPkg/IoMmuDxe/IoMmuBuffer.c index c8f6cf4818e8..103003cae376 100644 --- a/OvmfPkg/IoMmuDxe/IoMmuBuffer.c +++ b/OvmfPkg/IoMmuDxe/IoMmuBuffer.c @@ -367,7 +367,9 @@ IoMmuAllocateBounceBuffer ( { EFI_STATUS Status; UINT32 ReservedMemBitmap; + EFI_TPL OldTpl; + OldTpl = gBS->RaiseTPL (TPL_NOTIFY); ReservedMemBitmap = 0; Status = InternalAllocateBuffer ( Type, @@ -378,6 +380,7 @@ IoMmuAllocateBounceBuffer ( ); MapInfo->ReservedMemBitmap = ReservedMemBitmap; mReservedMemBitmap |= ReservedMemBitmap; + gBS->RestoreTPL (OldTpl); ASSERT (Status == EFI_SUCCESS); @@ -395,6 +398,8 @@ IoMmuFreeBounceBuffer ( IN OUT MAP_INFO *MapInfo ) { + EFI_TPL OldTpl; + if (MapInfo->ReservedMemBitmap == 0) { gBS->FreePages (MapInfo->PlainTextAddress, MapInfo->NumberOfPages); } else { @@ -407,9 +412,11 @@ IoMmuFreeBounceBuffer ( mReservedMemBitmap, mReservedMemBitmap & ((UINT32)(~MapInfo->ReservedMemBitmap)) )); + OldTpl = gBS->RaiseTPL (TPL_NOTIFY); MapInfo->PlainTextAddress = 0; mReservedMemBitmap &= (UINT32)(~MapInfo->ReservedMemBitmap); MapInfo->ReservedMemBitmap = 0; + gBS->RestoreTPL (OldTpl); } return EFI_SUCCESS; -- 2.41.0 -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#107057): https://edk2.groups.io/g/devel/message/107057 Mute This Topic: https://groups.io/mt/100238846/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
