OvmfPkg/VirtioFsDxe: introduce the basic FUSE request/response headers

Introduce the VIRTIO_FS_FUSE_REQUEST and VIRTIO_FS_FUSE_RESPONSE
structures, which are the common headers for the various FUSE
request/response structures.

Introduce the VirtioFsFuseNewRequest() helper function for populating
VIRTIO_FS_FUSE_REQUEST, from parameters and from a VIRTIO_FS-level request
counter.

Introduce the VirtioFsFuseCheckResponse() helper function for verifying
most FUSE response types that begin with the VIRTIO_FS_FUSE_RESPONSE
header.

Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3097
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20201216211125.19496-7-lersek@redhat.com>
Acked-by: Ard Biesheuvel <ard.biesheuvel@arm.com>

4 files changed, 287 insertions, 0 deletions

diff --git a/OvmfPkg/Include/IndustryStandard/VirtioFs.h b/OvmfPkg/Include/IndustryStandard/VirtioFs.h
index ea7d80d15d..521288b03f 100644
--- a/OvmfPkg/Include/IndustryStandard/VirtioFs.h
+++ b/OvmfPkg/Include/IndustryStandard/VirtioFs.h
@@ -49,4 +49,53 @@ typedef struct {
 } VIRTIO_FS_CONFIG;

 #pragma pack ()

 

+//

+// FUSE-related definitions follow.

+//

+// From virtio-v1.1-cs01-87fa6b5d8155, 5.11 File System Device: "[...] The

+// driver acts as the FUSE client mounting the file system. The virtio file

+// system device provides the mechanism for transporting FUSE requests [...]"

+//

+// Unfortunately, the documentation of the FUSE wire protocol is lacking. The

+// Virtio spec (as of this writing) simply defers to

+// "include/uapi/linux/fuse.h" in the Linux kernel source -- see the reference

+// in virtio spec file "introduction.tex", at commit 87fa6b5d8155.

+//

+// Of course, "include/uapi/linux/fuse.h" is a moving target (the virtio spec

+// does not specify a particular FUSE interface version). The OvmfPkg code

+// targets version 7.31, because that's the lowest version that the QEMU

+// virtio-fs daemon supports at this time -- see QEMU commit 72c42e2d6551

+// ("virtiofsd: Trim out compatibility code", 2020-01-23).

+//

+// Correspondingly, Linux's "include/uapi/linux/fuse.h" is consulted as checked

+// out at commit (c6ff213fe5b8^) = d78092e4937d ("fuse: fix page dereference

+// after free", 2020-09-18); that is, right before commit c6ff213fe5b8 ("fuse:

+// add submount support to <uapi/linux/fuse.h>", 2020-09-18) introduces FUSE

+// interface version 7.32.

+//

+#define VIRTIO_FS_FUSE_MAJOR  7

+#define VIRTIO_FS_FUSE_MINOR 31

+

+#pragma pack (1)

+//

+// Request-response headers common to all request types.

+//

+typedef struct {

+  UINT32 Len;

+  UINT32 Opcode;

+  UINT64 Unique;

+  UINT64 NodeId;

+  UINT32 Uid;

+  UINT32 Gid;

+  UINT32 Pid;

+  UINT32 Padding;

+} VIRTIO_FS_FUSE_REQUEST;

+

+typedef struct {

+  UINT32 Len;

+  INT32  Error;

+  UINT64 Unique;

+} VIRTIO_FS_FUSE_RESPONSE;

+#pragma pack ()

+

 #endif // VIRTIO_FS_H_

diff --git a/OvmfPkg/VirtioFsDxe/DriverBinding.c b/OvmfPkg/VirtioFsDxe/DriverBinding.c
index b888158a80..4a2787a50a 100644
--- a/OvmfPkg/VirtioFsDxe/DriverBinding.c
+++ b/OvmfPkg/VirtioFsDxe/DriverBinding.c
@@ -84,6 +84,11 @@ VirtioFsBindingStart (
     goto CloseVirtio;

   }

 

+  //

+  // Initialize the FUSE request counter.

+  //

+  VirtioFs->RequestId = 1;

+

   Status = gBS->CreateEvent (EVT_SIGNAL_EXIT_BOOT_SERVICES, TPL_CALLBACK,

                   VirtioFsExitBoot, VirtioFs, &VirtioFs->ExitBoot);

   if (EFI_ERROR (Status)) {

diff --git a/OvmfPkg/VirtioFsDxe/Helpers.c b/OvmfPkg/VirtioFsDxe/Helpers.c
index c493f6068f..8444891907 100644
--- a/OvmfPkg/VirtioFsDxe/Helpers.c
+++ b/OvmfPkg/VirtioFsDxe/Helpers.c
@@ -698,3 +698,219 @@ Unmap:
 

   return Status;

 }

+

+/**

+  Set up the fields of a new VIRTIO_FS_FUSE_REQUEST object.

+

+  The function may only be called after VirtioFsInit() returns successfully and

+  before VirtioFsUninit() is called.

+

+  @param[in,out] VirtioFs The Virtio Filesystem device that the request is

+                          being prepared for. The "VirtioFs->RequestId" field

+                          will be copied into "Request->Unique". On output (on

+                          successful return), "VirtioFs->RequestId" will be

+                          incremented.

+

+  @param[out] Request     The VIRTIO_FS_FUSE_REQUEST object whose fields are to

+                          be set.

+

+  @param[in] RequestSize  The total size of the request, including

+                          sizeof(VIRTIO_FS_FUSE_REQUEST).

+

+  @param[in] Opcode       The VIRTIO_FS_FUSE_OPCODE that identifies the command

+                          to send.

+

+  @param[in] NodeId       The inode number of the file that the request refers

+                          to.

+

+  @retval EFI_INVALID_PARAMETER  RequestSize is smaller than

+                                 sizeof(VIRTIO_FS_FUSE_REQUEST).

+

+  @retval EFI_OUT_OF_RESOURCES   "VirtioFs->RequestId" is MAX_UINT64, and can

+                                 be incremented no more.

+

+  @retval EFI_SUCCESS            Request has been populated,

+                                 "VirtioFs->RequestId" has been incremented.

+**/

+EFI_STATUS

+VirtioFsFuseNewRequest (

+  IN OUT VIRTIO_FS              *VirtioFs,

+     OUT VIRTIO_FS_FUSE_REQUEST *Request,

+  IN     UINT32                 RequestSize,

+  IN     UINT32                 Opcode,

+  IN     UINT64                 NodeId

+  )

+{

+  if (RequestSize < sizeof *Request) {

+    return EFI_INVALID_PARAMETER;

+  }

+

+  if (VirtioFs->RequestId == MAX_UINT64) {

+    return EFI_OUT_OF_RESOURCES;

+  }

+

+  Request->Len     = RequestSize;

+  Request->Opcode  = Opcode;

+  Request->Unique  = VirtioFs->RequestId++;

+  Request->NodeId  = NodeId;

+  Request->Uid     = 0;

+  Request->Gid     = 0;

+  Request->Pid     = 1;

+  Request->Padding = 0;

+

+  return EFI_SUCCESS;

+}

+

+/**

+  Check the common FUSE response format.

+

+  The first buffer in the response scatter-gather list is assumed a

+  VIRTIO_FS_FUSE_RESPONSE structure. Subsequent response buffers, if any, up to

+  and excluding the last one, are assumed fixed size. The last response buffer

+  may or may not be fixed size, as specified by the caller.

+

+  This function may only be called after VirtioFsSgListsSubmit() returns

+  successfully.

+

+  @param[in] ResponseSgList   The scatter-gather list that describes the

+                              response part of the exchange -- the buffers that

+                              the Virtio Filesystem device filled in during the

+                              virtio transfer.

+

+  @param[in] RequestId        The request identifier to which the response is

+                              expected to belong.

+

+  @param[out] TailBufferFill  If NULL, then the last buffer in ResponseSgList

+                              is considered fixed size. Otherwise, the last

+                              buffer is considered variable size, and on

+                              successful return, TailBufferFill reports the

+                              number of bytes in the last buffer.

+

+  @retval EFI_INVALID_PARAMETER  TailBufferFill is not NULL (i.e., the last

+                                 buffer is considered variable size), and

+                                 ResponseSgList->NumVec is 1.

+

+  @retval EFI_INVALID_PARAMETER  The allocated size of the first buffer does

+                                 not match sizeof(VIRTIO_FS_FUSE_RESPONSE).

+

+  @retval EFI_PROTOCOL_ERROR     The VIRTIO_FS_FUSE_RESPONSE structure in the

+                                 first buffer has not been fully populated.

+

+  @retval EFI_PROTOCOL_ERROR     "VIRTIO_FS_FUSE_RESPONSE.Len" in the first

+                                 buffer does not equal the sum of the

+                                 individual buffer sizes (as populated).

+

+  @retval EFI_PROTOCOL_ERROR     "VIRTIO_FS_FUSE_RESPONSE.Unique" in the first

+                                 buffer does not equal RequestId.

+

+  @retval EFI_PROTOCOL_ERROR     "VIRTIO_FS_FUSE_RESPONSE.Error" in the first

+                                 buffer is zero, but a subsequent fixed size

+                                 buffer has not been fully populated.

+

+  @retval EFI_DEVICE_ERROR       "VIRTIO_FS_FUSE_RESPONSE.Error" in the first

+                                 buffer is nonzero. The caller may investigate

+                                 "VIRTIO_FS_FUSE_RESPONSE.Error". Note that the

+                                 completeness of the subsequent fixed size

+                                 buffers is not verified in this case.

+

+  @retval EFI_SUCCESS            Verification successful.

+**/

+EFI_STATUS

+VirtioFsFuseCheckResponse (

+  IN  VIRTIO_FS_SCATTER_GATHER_LIST *ResponseSgList,

+  IN  UINT64                        RequestId,

+  OUT UINTN                         *TailBufferFill

+  )

+{

+  UINTN                   NumFixedSizeVec;

+  VIRTIO_FS_FUSE_RESPONSE *CommonResp;

+  UINT32                  TotalTransferred;

+  UINTN                   Idx;

+

+  //

+  // Ensured by VirtioFsSgListsValidate().

+  //

+  ASSERT (ResponseSgList->NumVec > 0);

+

+  if (TailBufferFill == NULL) {

+    //

+    // All buffers are considered fixed size.

+    //

+    NumFixedSizeVec = ResponseSgList->NumVec;

+  } else {

+    //

+    // If the last buffer is variable size, then we need that buffer to be

+    // different from the first buffer, which is considered a

+    // VIRTIO_FS_FUSE_RESPONSE (fixed size) structure.

+    //

+    if (ResponseSgList->NumVec == 1) {

+      return EFI_INVALID_PARAMETER;

+    }

+    NumFixedSizeVec = ResponseSgList->NumVec - 1;

+  }

+

+  //

+  // The first buffer is supposed to carry a (fully populated)

+  // VIRTIO_FS_FUSE_RESPONSE structure.

+  //

+  if (ResponseSgList->IoVec[0].Size != sizeof *CommonResp) {

+    return EFI_INVALID_PARAMETER;

+  }

+  if (ResponseSgList->IoVec[0].Transferred != ResponseSgList->IoVec[0].Size) {

+    return EFI_PROTOCOL_ERROR;

+  }

+

+  //

+  // FUSE must report the same number of bytes, written by the Virtio

+  // Filesystem device, as the virtio transport does.

+  //

+  CommonResp = ResponseSgList->IoVec[0].Buffer;

+  TotalTransferred = 0;

+  for (Idx = 0; Idx < ResponseSgList->NumVec; Idx++) {

+    //

+    // Integer overflow and truncation are not possible, based on

+    // VirtioFsSgListsValidate() and VirtioFsSgListsSubmit().

+    //

+    TotalTransferred += (UINT32)ResponseSgList->IoVec[Idx].Transferred;

+  }

+  if (CommonResp->Len != TotalTransferred) {

+    return EFI_PROTOCOL_ERROR;

+  }

+

+  //

+  // Enforce that FUSE match our request ID in the response.

+  //

+  if (CommonResp->Unique != RequestId) {

+    return EFI_PROTOCOL_ERROR;

+  }

+

+  //

+  // If there is an explicit error report, skip checking the transfer

+  // counts for the rest of the fixed size buffers.

+  //

+  if (CommonResp->Error != 0) {

+    return EFI_DEVICE_ERROR;

+  }

+

+  //

+  // There was no error reported, so we require that the Virtio Filesystem

+  // device populate all fixed size buffers. We checked this for the very first

+  // buffer above; let's check the rest (if any).

+  //

+  ASSERT (NumFixedSizeVec >= 1);

+  for (Idx = 1; Idx < NumFixedSizeVec; Idx++) {

+    if (ResponseSgList->IoVec[Idx].Transferred !=

+        ResponseSgList->IoVec[Idx].Size) {

+      return EFI_PROTOCOL_ERROR;

+    }

+  }

+

+  //

+  // If the last buffer is considered variable size, report its filled size.

+  //

+  if (TailBufferFill != NULL) {

+    *TailBufferFill = ResponseSgList->IoVec[NumFixedSizeVec].Transferred;

+  }

+

+  return EFI_SUCCESS;

+}

diff --git a/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h b/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h
index 12acbd6dc3..f7eae9a4b7 100644
--- a/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h
+++ b/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h
@@ -44,6 +44,7 @@ typedef struct {
   UINT16                          QueueSize; // VirtioFsInit        1

   VRING                           Ring;      // VirtioRingInit      2

   VOID                            *RingMap;  // VirtioRingMap       2

+  UINT64                          RequestId; // DriverBindingStart  0

   EFI_EVENT                       ExitBoot;  // DriverBindingStart  0

   EFI_SIMPLE_FILE_SYSTEM_PROTOCOL SimpleFs;  // DriverBindingStart  0

 } VIRTIO_FS;

@@ -132,6 +133,22 @@ VirtioFsSgListsSubmit (
   IN OUT VIRTIO_FS_SCATTER_GATHER_LIST *ResponseSgList OPTIONAL

   );

 

+EFI_STATUS

+VirtioFsFuseNewRequest (

+  IN OUT VIRTIO_FS              *VirtioFs,

+     OUT VIRTIO_FS_FUSE_REQUEST *Request,

+  IN     UINT32                 RequestSize,

+  IN     UINT32                 Opcode,

+  IN     UINT64                 NodeId

+  );

+

+EFI_STATUS

+VirtioFsFuseCheckResponse (

+  IN  VIRTIO_FS_SCATTER_GATHER_LIST *ResponseSgList,

+  IN  UINT64                        RequestId,

+  OUT UINTN                         *TailBufferFill

+  );

+

 //

 // EFI_SIMPLE_FILE_SYSTEM_PROTOCOL member functions for the Virtio Filesystem

 // driver.