[edk2-devel] [edk2 PATCH 42/48] OvmfPkg/VirtioFsDxe: add helper for composing rename/move destination path
Ard Biesheuvel
ard.biesheuvel at arm.com
Fri Dec 18 17:39:39 UTC 2020
On 12/16/20 10:11 PM, Laszlo Ersek wrote:
> The EFI_FILE_PROTOCOL.SetInfo() member is somewhat under-specified; one of
> its modes of operation is renaming/moving the file.
>
> In order to create the destination pathname in canonical format, 2*2=4
> cases have to be considered. For the sake of discussion, assume the
> current canonical pathname of a VIRTIO_FS_FILE is "/home/user/f1.txt".
> Then, consider the following rename/move requests from
> EFI_FILE_PROTOCOL.SetInfo():
>
> Destination requested Destination Move into Destination in
> by SetInfo() relative? directory? canonical format
> --------------------- ----------- ---------- -----------------------
> L"\\dir\\f2.txt" no no "/dir/f2.txt"
What happens in the above case if /dir/f2.txt is an existing directory?
> L"\\dir\\" no yes "/dir/f1.txt"
> L"dir\\f2.txt" yes no "/home/user/dir/f2.txt"
> L"dir\\" yes yes "/home/user/dir/f1.txt"
>
> Add the VirtioFsComposeRenameDestination() function, for composing the
> last column from the current canonical pathname and the SetInfo() input.
>
> The function works on the following principles:
>
> - The prefix of the destination path is "/", if the SetInfo() rename
> request is absolute.
>
> Otherwise, the dest prefix is the "current directory" (the most specific
> parent directory) of the original pathname (in the above example,
> "/home/user").
>
> - The suffix of the destination path is precisely the SetInfo() request
> string, if the "move into directory" convenience format -- the trailing
> backslash -- is not used. (In the above example, L"\\dir\\f2.txt" and
> L"dir\\f2.txt".)
>
> Otherwise, the suffix is the SetInfo() request, plus the original
> basename (in the above example, L"\\dir\\f1.txt" and L"dir\\f1.txt").
>
> - The complete destination is created by fusing the dest prefix and the
> dest suffix, using the VirtioFsAppendPath() function.
>
> Cc: Ard Biesheuvel <ard.biesheuvel at arm.com>
> Cc: Jordan Justen <jordan.l.justen at intel.com>
> Cc: Philippe Mathieu-Daudé <philmd at redhat.com>
> Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=3097
> Signed-off-by: Laszlo Ersek <lersek at redhat.com>
> ---
> OvmfPkg/VirtioFsDxe/VirtioFsDxe.h | 8 +
> OvmfPkg/VirtioFsDxe/Helpers.c | 194 ++++++++++++++++++++
> 2 files changed, 202 insertions(+)
>
> diff --git a/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h b/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h
> index 9334e5434c51..a6dfac71f4a7 100644
> --- a/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h
> +++ b/OvmfPkg/VirtioFsDxe/VirtioFsDxe.h
> @@ -257,16 +257,24 @@ VirtioFsLookupMostSpecificParentDir (
>
> EFI_STATUS
> VirtioFsGetBasename (
> IN CHAR8 *Path,
> OUT CHAR16 *Basename OPTIONAL,
> IN OUT UINTN *BasenameSize
> );
>
> +EFI_STATUS
> +VirtioFsComposeRenameDestination (
> + IN CHAR8 *LhsPath8,
> + IN CHAR16 *RhsPath16,
> + OUT CHAR8 **ResultPath8,
> + OUT BOOLEAN *RootEscape
> + );
> +
> EFI_STATUS
> VirtioFsFuseAttrToEfiFileInfo (
> IN VIRTIO_FS_FUSE_ATTRIBUTES_RESPONSE *FuseAttr,
> OUT EFI_FILE_INFO *FileInfo
> );
>
> EFI_STATUS
> VirtioFsFuseDirentPlusToEfiFileInfo (
> diff --git a/OvmfPkg/VirtioFsDxe/Helpers.c b/OvmfPkg/VirtioFsDxe/Helpers.c
> index cdaa8557a17b..b741cf753495 100644
> --- a/OvmfPkg/VirtioFsDxe/Helpers.c
> +++ b/OvmfPkg/VirtioFsDxe/Helpers.c
> @@ -1778,16 +1778,210 @@ VirtioFsGetBasename (
> }
>
> for (Idx = LastComponent; Idx < PathSize; Idx++) {
> Basename[Idx - LastComponent] = Path[Idx];
> }
> return EFI_SUCCESS;
> }
>
> +/**
> + Format the destination of a rename/move operation as a dynamically allocated
> + canonical pathname.
> +
> + Any dot-dot in RhsPath16 that would remove the root directory is dropped, and
> + reported through RootEscape, without failing the function call.
> +
> + @param[in] LhsPath8 The source pathname operand of the rename/move
> + operation, expressed as a canonical pathname (as
> + defined in the description of VirtioFsAppendPath()).
> + The root directory "/" cannot be renamed/moved, and
> + will be rejected.
> +
> + @param[in] RhsPath16 The destination pathname operand expressed as a
> + UEFI-style CHAR16 pathname.
> +
> + If RhsPath16 starts with a backslash, then RhsPath16
> + is considered absolute. Otherwise, RhsPath16 is
> + interpreted relative to the most specific parent
> + directory found in LhsPath8.
> +
> + Independently, if RhsPath16 ends with a backslash
> + (i.e., RhsPath16 is given in the "move into
> + directory" convenience form), then RhsPath16 is
> + interpreted with the basename of LhsPath8 appended.
> + Otherwise, the last pathname component of RhsPath16
> + is taken as the last pathname component of the
> + rename/move destination.
> +
> + An empty RhsPath16 is rejected.
> +
> + @param[out] ResultPath8 The POSIX-style, canonical format pathname that
> + leads to the renamed/moved file. After use, the
> + caller is responsible for freeing ResultPath8.
> +
> + @param[out] RootEscape Set to TRUE if at least one dot-dot component in
> + RhsPath16 attempted to escape the root directory;
> + set to FALSE otherwise.
> +
> + @retval EFI_SUCCESS ResultPath8 has been produced. RootEscape has
> + been output.
> +
> + @retval EFI_INVALID_PARAMETER LhsPath8 is "/".
> +
> + @retval EFI_INVALID_PARAMETER RhsPath16 is zero-length.
> +
> + @retval EFI_INVALID_PARAMETER RhsPath16 failed the
> + VIRTIO_FS_MAX_PATHNAME_LENGTH check.
> +
> + @retval EFI_OUT_OF_RESOURCES Memory allocation failed.
> +
> + @retval EFI_OUT_OF_RESOURCES ResultPath8 would have failed the
> + VIRTIO_FS_MAX_PATHNAME_LENGTH check.
> +
> + @retval EFI_UNSUPPORTED RhsPath16 contains a character that either
> + falls outside of the printable ASCII set, or
> + is a forward slash.
> +**/
> +EFI_STATUS
> +VirtioFsComposeRenameDestination (
> + IN CHAR8 *LhsPath8,
> + IN CHAR16 *RhsPath16,
> + OUT CHAR8 **ResultPath8,
> + OUT BOOLEAN *RootEscape
> + )
> +{
> + //
> + // Lengths are expressed as numbers of characters (CHAR8 or CHAR16),
> + // excluding terminating NULs. Sizes are expressed as byte counts, including
> + // the bytes taken up by terminating NULs.
> + //
> + UINTN RhsLen;
> + UINTN LhsBasename16Size;
> + EFI_STATUS Status;
> + UINTN LhsBasenameLen;
> + UINTN DestSuffix16Size;
> + CHAR16 *DestSuffix16;
> + CHAR8 *DestPrefix8;
> +
> + //
> + // An empty destination operand for the rename/move operation is not allowed.
> + //
> + RhsLen = StrLen (RhsPath16);
> + if (RhsLen == 0) {
> + return EFI_INVALID_PARAMETER;
> + }
> + //
> + // Enforce length restriction on RhsPath16.
> + //
> + if (RhsLen > VIRTIO_FS_MAX_PATHNAME_LENGTH) {
> + return EFI_INVALID_PARAMETER;
> + }
> +
> + //
> + // Determine the length of the basename of LhsPath8.
> + //
> + LhsBasename16Size = 0;
> + Status = VirtioFsGetBasename (LhsPath8, NULL, &LhsBasename16Size);
> + ASSERT (Status == EFI_BUFFER_TOO_SMALL);
> + ASSERT (LhsBasename16Size >= sizeof (CHAR16));
> + ASSERT (LhsBasename16Size % sizeof (CHAR16) == 0);
> + LhsBasenameLen = LhsBasename16Size / sizeof (CHAR16) - 1;
> + if (LhsBasenameLen == 0) {
> + //
> + // The root directory cannot be renamed/moved.
> + //
> + return EFI_INVALID_PARAMETER;
> + }
> +
> + //
> + // Resolve the "move into directory" convenience form in RhsPath16.
> + //
> + if (RhsPath16[RhsLen - 1] == L'\\') {
> + //
> + // Append the basename of LhsPath8 as a CHAR16 string to RhsPath16.
> + //
> + DestSuffix16Size = RhsLen * sizeof (CHAR16) + LhsBasename16Size;
> + DestSuffix16 = AllocatePool (DestSuffix16Size);
> + if (DestSuffix16 == NULL) {
> + return EFI_OUT_OF_RESOURCES;
> + }
> + CopyMem (DestSuffix16, RhsPath16, RhsLen * sizeof (CHAR16));
> + Status = VirtioFsGetBasename (LhsPath8, DestSuffix16 + RhsLen,
> + &LhsBasename16Size);
> + ASSERT_EFI_ERROR (Status);
> + } else {
> + //
> + // Just create a copy of RhsPath16.
> + //
> + DestSuffix16Size = (RhsLen + 1) * sizeof (CHAR16);
> + DestSuffix16 = AllocateCopyPool (DestSuffix16Size, RhsPath16);
> + if (DestSuffix16 == NULL) {
> + return EFI_OUT_OF_RESOURCES;
> + }
> + }
> +
> + //
> + // If the destination operand is absolute, it will be interpreted relative to
> + // the root directory.
> + //
> + // Otherwise (i.e., if the destination operand is relative), then create the
> + // canonical pathname that the destination operand is interpreted relatively
> + // to; that is, the canonical pathname of the most specific parent directory
> + // found in LhsPath8.
> + //
> + if (DestSuffix16[0] == L'\\') {
> + DestPrefix8 = AllocateCopyPool (sizeof "/", "/");
> + if (DestPrefix8 == NULL) {
> + Status = EFI_OUT_OF_RESOURCES;
> + goto FreeDestSuffix16;
> + }
> + } else {
> + UINTN LhsLen;
> + UINTN DestPrefixLen;
> +
> + //
> + // Strip the basename of LhsPath8.
> + //
> + LhsLen = AsciiStrLen (LhsPath8);
> + ASSERT (LhsBasenameLen < LhsLen);
> + DestPrefixLen = LhsLen - LhsBasenameLen;
> + ASSERT (LhsPath8[DestPrefixLen - 1] == '/');
> + //
> + // If we're not at the root directory, strip the slash too.
> + //
> + if (DestPrefixLen > 1) {
> + DestPrefixLen--;
> + }
> + DestPrefix8 = AllocatePool (DestPrefixLen + 1);
> + if (DestPrefix8 == NULL) {
> + Status = EFI_OUT_OF_RESOURCES;
> + goto FreeDestSuffix16;
> + }
> + CopyMem (DestPrefix8, LhsPath8, DestPrefixLen);
> + DestPrefix8[DestPrefixLen] = '\0';
> + }
> +
> + //
> + // Now combine DestPrefix8 and DestSuffix16 into the final canonical
> + // pathname.
> + //
> + Status = VirtioFsAppendPath (DestPrefix8, DestSuffix16, ResultPath8,
> + RootEscape);
> +
> + FreePool (DestPrefix8);
> + //
> + // Fall through.
> + //
> +FreeDestSuffix16:
> + FreePool (DestSuffix16);
> +
> + return Status;
> +}
> +
> /**
> Convert select fields of a VIRTIO_FS_FUSE_ATTRIBUTES_RESPONSE object to
> corresponding fields in EFI_FILE_INFO.
>
> @param[in] FuseAttr The VIRTIO_FS_FUSE_ATTRIBUTES_RESPONSE object to
> convert the relevant fields from.
>
> @param[out] FileInfo The EFI_FILE_INFO structure to modify. Importantly, the
>
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