Re: [edk2-platforms][PATCH v4 1/2] Ext4Pkg: Add symbolic links support

["Pedro Falcato" <pedro.falcato@gmail.com>]

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Hi Savva,

Sorry for the huge delay. Comments inline.

On Thu, Jul 28, 2022 at 4:26 PM Savva Mitrofanov <savvamtr@gmail.com> wrote:

> BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=3677
>
> Provided support for symlink file type. Added routine which allows
> reading and following them through recursive open() call. As a security
> meausure implemented simple symlink loop check with nest level limit
> equal 8. Also this patch moves Ext4Open functionality to internal
> routine.
>
> Cc: Marvin Häuser <mhaeuser@posteo.de>
> Cc: Pedro Falcato <pedro.falcato@gmail.com>
> Cc: Vitaly Cheptsov <vit9696@protonmail.com>
> Signed-off-by: Savva Mitrofanov <savvamtr@gmail.com>
> ---
>  Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h |  13 +-
>  Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h  |  98 +++++-
>  Features/Ext4Pkg/Ext4Dxe/File.c     | 359 ++++++++++++++++++--
>  Features/Ext4Pkg/Ext4Dxe/Inode.c    |  53 +++
>  4 files changed, 485 insertions(+), 38 deletions(-)
>
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> b/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> index a55cd2fa68ad..a73e3f8622f1 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> @@ -171,7 +171,7 @@
>  #define EXT4_DIRTY_FL         0x00000100
>  #define EXT4_COMPRBLK_FL      0x00000200
>  #define EXT4_NOCOMPR_FL       0x00000400
> -#define EXT4_ECOMPR_FL        0x00000800
> +#define EXT4_ENCRYPT_FL       0x00000800
>  #define EXT4_BTREE_FL         0x00001000
>  #define EXT4_INDEX_FL         0x00002000
>  #define EXT4_JOURNAL_DATA_FL  0x00004000
> @@ -332,11 +332,12 @@ STATIC_ASSERT (
>    "ext4 block group descriptor struct has incorrect size"
>    );
>
> -#define EXT4_DBLOCKS     12
> -#define EXT4_IND_BLOCK   12
> -#define EXT4_DIND_BLOCK  13
> -#define EXT4_TIND_BLOCK  14
> -#define EXT4_NR_BLOCKS   15
> +#define EXT4_DBLOCKS                12
> +#define EXT4_IND_BLOCK              12
> +#define EXT4_DIND_BLOCK             13
> +#define EXT4_TIND_BLOCK             14
> +#define EXT4_NR_BLOCKS              15
> +#define EXT4_FAST_SYMLINK_MAX_SIZE  EXT4_NR_BLOCKS * sizeof(UINT32)
>
>  #define EXT4_GOOD_OLD_INODE_SIZE  128
>
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> index b1508482b0a7..c1df9d1149e4 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> @@ -31,7 +31,9 @@
>
>  #include "Ext4Disk.h"
>
> +#define SYMLOOP_MAX    8
>
I'm scared that this may not be enough. Could we use 40 here as Linux does?

>  #define EXT4_NAME_MAX  255
> +#define EFI_PATH_MAX   4096
>
Don't use EFI_* in Ext4Dxe code, so prefix this with EXT4_ instead maybe?

>
>  #define EXT4_DRIVER_VERSION  0x0000
>
> @@ -324,11 +326,11 @@ number of read bytes.
>  **/
>  EFI_STATUS
>  Ext4Read (
> -  IN EXT4_PARTITION  *Partition,
> -  IN EXT4_FILE       *File,
> -  OUT VOID           *Buffer,
> -  IN UINT64          Offset,
> -  IN OUT UINTN       *Length
> +  IN     EXT4_PARTITION  *Partition,
> +  IN     EXT4_FILE       *File,
> +  OUT    VOID            *Buffer,
> +  IN     UINT64          Offset,
> +  IN OUT UINTN           *Length
>    );
>
>  /**
> @@ -368,6 +370,7 @@ struct _Ext4File {
>
>    UINT64                OpenMode;
>    UINT64                Position;
> +  UINT32                SymLoops;
>
>    EXT4_PARTITION        *Partition;
>
> @@ -497,6 +500,45 @@ Ext4SetupFile (
>    IN EXT4_PARTITION  *Partition
>    );
>
> +/**
> +  Opens a new file relative to the source file's location.
> +
> +  @param[out] FoundFile  A pointer to the location to return the opened
> handle for the new
> +                         file.
> +  @param[in]  Source     A pointer to the EXT4_FILE instance that is the
> file
> +                         handle to the source location. This would
> typically be an open
> +                         handle to a directory.
> +  @param[in]  FileName   The Null-terminated string of the name of the
> file to be opened.
> +                         The file name may contain the following path
> modifiers: "\", ".",
> +                         and "..".
> +  @param[in]  OpenMode   The mode to open the file. The only valid
> combinations that the
> +                         file may be opened with are: Read, Read/Write,
> or Create/Read/Write.
> +  @param[in]  Attributes Only valid for EFI_FILE_MODE_CREATE, in which
> case these are the
> +                         attribute bits for the newly created file.
> +
> +  @retval EFI_SUCCESS          The file was opened.
> +  @retval EFI_NOT_FOUND        The specified file could not be found on
> the device.
> +  @retval EFI_NO_MEDIA         The device has no medium.
> +  @retval EFI_MEDIA_CHANGED    The device has a different medium in it or
> the medium is no
> +                               longer supported.
> +  @retval EFI_DEVICE_ERROR     The device reported an error.
> +  @retval EFI_VOLUME_CORRUPTED The file system structures are corrupted.
> +  @retval EFI_WRITE_PROTECTED  An attempt was made to create a file, or
> open a file for write
> +                               when the media is write-protected.
> +  @retval EFI_ACCESS_DENIED    The service denied access to the file.
> +  @retval EFI_OUT_OF_RESOURCES Not enough resources were available to
> open the file.
> +  @retval EFI_VOLUME_FULL      The volume is full.
> +
> +**/
> +EFI_STATUS
> +Ext4OpenInternal (
> +  OUT EXT4_FILE  **FoundFile,
>
First IN parameters, then OUT parameters.

> +  IN  EXT4_FILE  *Source,
> +  IN  CHAR16     *FileName,
> +  IN  UINT64     OpenMode,
> +  IN  UINT64     Attributes
> +  );
> +
>  /**
>     Closes a file.
>
> @@ -774,6 +816,30 @@ Ext4FileIsDir (
>    IN CONST EXT4_FILE  *File
>    );
>
> +/**
> +   Checks if a file is a symlink.
> +
> +   @param[in]      File          Pointer to the opened file.
> +
> +   @return BOOLEAN         Whether file is a symlink
> +**/
> +BOOLEAN
> +Ext4FileIsSymlink (
> +  IN CONST EXT4_FILE  *File
> +  );
> +
> +/**
> +   Detects if a symlink is a fast symlink.
> +
> +   @param[in]      File          Pointer to the opened file.
> +
> +   @return BOOLEAN         Whether symlink is a fast symlink
> +**/
> +BOOLEAN
> +Ext4SymlinkIsFastSymlink (
> +  IN CONST EXT4_FILE  *File
> +  );
>
Does this need to be in Ext4Dxe.h? This is pretty symlink specific.

> +
>  /**
>     Checks if a file is a regular file.
>     @param[in]      File          Pointer to the opened file.
> @@ -797,7 +863,7 @@ Ext4FileIsReg (
>             it's a regular file or a directory, since most other file types
>             don't make sense under UEFI.
>  **/
> -#define Ext4FileIsOpenable(File)  (Ext4FileIsReg(File) ||
> Ext4FileIsDir(File))
> +#define Ext4FileIsOpenable(File)  (Ext4FileIsReg (File) || Ext4FileIsDir
> (File) || Ext4FileIsSymlink (File))
>
>  #define EXT4_INODE_HAS_FIELD(Inode, Field)
>      \
>    (Inode->i_extra_isize + EXT4_GOOD_OLD_INODE_SIZE >=
>       \
> @@ -935,6 +1001,26 @@ Ext4ReadDir (
>    IN OUT UINTN       *OutLength
>    );
>
> +/**
> +  Reads a symlink file.
> +
> +  @param[in]      Partition   Pointer to the ext4 partition.
> +  @param[in]      File        Pointer to the open symlink file.
> +  @param[out]     Symlink     Pointer to the output unicode symlink
> string.
> +
> +  @retval EFI_SUCCESS           Symlink was read.
> +  @retval EFI_ACCESS_DENIED     Symlink is encrypted.
> +  @retval EFI_OUT_OF_RESOURCES  Memory allocation error.
> +  @retval EFI_INVALID_PARAMETER Symlink path has incorrect length
> +  @retval EFI_VOLUME_CORRUPTED  Symlink read block size differ from inode
> value
> +**/
> +EFI_STATUS
> +Ext4ReadSymlink (
> +  IN     EXT4_PARTITION  *Partition,
> +  IN     EXT4_FILE       *File,
> +  OUT    CHAR16          **Symlink
> +  );
> +
>  /**
>     Initialises the (empty) extents map, that will work as a cache of
> extents.
>
> diff --git a/Features/Ext4Pkg/Ext4Dxe/File.c
> b/Features/Ext4Pkg/Ext4Dxe/File.c
> index ff1746d5640a..ae9230d6422b 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/File.c
> +++ b/Features/Ext4Pkg/Ext4Dxe/File.c
> @@ -134,14 +134,224 @@ Ext4DirCanLookup (
>    return (File->Inode->i_mode & EXT4_INO_PERM_EXEC_OWNER) ==
> EXT4_INO_PERM_EXEC_OWNER;
>  }
>
> +/**
> +  Reads a fast symlink file.
> +
> +  @param[in]      Partition   Pointer to the ext4 partition.
> +  @param[in]      File        Pointer to the open symlink file.
> +  @param[out]     AsciiSymlink     Pointer to the output ascii symlink
> string.
> +  @param[out]     AsciiSymlinkSize Pointer to the output ascii symlink
> string length.
> +
> +  @retval EFI_SUCCESS            Fast symlink was read.
> +  @retval EFI_OUT_OF_RESOURCES   Memory allocation error.
> +**/
> +STATIC
> +EFI_STATUS
> +Ext4ReadFastSymlink (
> +  IN     EXT4_PARTITION  *Partition,
> +  IN     EXT4_FILE       *File,
> +  OUT    CHAR8           **AsciiSymlink,
> +  OUT    UINT32          *AsciiSymlinkSize
> +  )
> +{
> +  UINT32  SymlinkSize;
> +  CHAR8   *AsciiSymlinkTmp;
> +  //
> +  // Fast-symlink's EXT4_INODE_SIZE is not necessarily validated when we
> checked it in
> +  // Ext4SymlinkIsFastSymlink(), so truncate if necessary.
> +  //
>
I think the correct solution here is to check if the inode size fits in
EXT4_FAST_SYMLINK_MAX_SIZE in Ext4SymlinkIsFastSymlink. Or possibly check
it here and error-out (blatant corruption).
Truncating doesn't seem correct.

> +  SymlinkSize = (UINT32)MIN (EXT4_INODE_SIZE (File->Inode),
> EXT4_FAST_SYMLINK_MAX_SIZE);
> +
> +  AsciiSymlinkTmp = AllocatePool (SymlinkSize + 1);
> +  if (AsciiSymlinkTmp == NULL) {
> +    DEBUG ((DEBUG_FS, "[ext4] Failed to allocate symlink ascii string
> buffer\n"));
>
Nit: DEBUG_ERROR?

> +    return EFI_OUT_OF_RESOURCES;
> +  }
> +
> +  CopyMem (AsciiSymlinkTmp, File->Inode->i_data, SymlinkSize);
> +
> +  //
> +  // Add null-terminator
> +  //
> +  AsciiSymlinkTmp[SymlinkSize] = '\0';
> +
> +  *AsciiSymlink     = AsciiSymlinkTmp;
> +  *AsciiSymlinkSize = SymlinkSize + 1;
> +
> +  return EFI_SUCCESS;
> +}
> +
> +/**
> +  Reads a slow symlink file.
> +
> +  @param[in]      Partition        Pointer to the ext4 partition.
> +  @param[in]      File             Pointer to the open symlink file.
> +  @param[out]     AsciiSymlink     Pointer to the output ascii symlink
> string.
> +  @param[out]     AsciiSymlinkSize Pointer to the output ascii symlink
> string length.
> +
> +  @retval EFI_SUCCESS           Slow symlink was read.
> +  @retval EFI_OUT_OF_RESOURCES  Memory allocation error.
> +  @retval EFI_INVALID_PARAMETER Slow symlink path has incorrect length
> +  @retval EFI_VOLUME_CORRUPTED  Symlink read block size differ from inode
> value
> +**/
> +STATIC
> +EFI_STATUS
> +Ext4ReadSlowSymlink (
> +  IN     EXT4_PARTITION  *Partition,
> +  IN     EXT4_FILE       *File,
> +  OUT    CHAR8           **AsciiSymlink,
> +  OUT    UINT32          *AsciiSymlinkSize
> +  )
> +{
> +  EFI_STATUS  Status;
> +  CHAR8       *SymlinkTmp;
> +  UINT64      SymlinkSizeTmp;
> +  UINT32      SymlinkAllocateSize;
> +  UINTN       ReadSize;
> +
> +  SymlinkSizeTmp = EXT4_INODE_SIZE (File->Inode);
> +
> +  //
> +  // Allocate EXT4_INODE_SIZE + 1
> +  //
> +  if (SymlinkSizeTmp > EFI_PATH_MAX - 1) {
>
Why is this > EFI_PATH_MAX - 1 and not >= EFI_PATH_MAX? Also, why does the
inode size need to be strictly smaller than EFI_PATH_MAX?

> +    DEBUG ((
> +      DEBUG_FS,
>
Nit: DEBUG_ERROR?

> +      "[ext4] Error! Symlink path maximum length was hit!\n"
> +      ));
> +    return EFI_INVALID_PARAMETER;
> +  }
> +
> +  SymlinkAllocateSize = (UINT32)SymlinkSizeTmp + 1;
> +
> +  SymlinkTmp = AllocatePool (SymlinkAllocateSize);
> +  if (SymlinkTmp == NULL) {
> +    DEBUG ((DEBUG_FS, "[ext4] Failed to allocate symlink ascii string
> buffer\n"));
> +    return EFI_OUT_OF_RESOURCES;
> +  }
> +

+  ReadSize = (UINTN)SymlinkSizeTmp;
> +  Status   = Ext4Read (Partition, File, SymlinkTmp, File->Position,
> &ReadSize);
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_FS, "[ext4] Failed to read symlink from blocks with
> Status %r\n", Status));
>
Nit: lowercase "status" in the DEBUG.

> +    FreePool (SymlinkTmp);
> +    return Status;
> +  }
> +
> +  File->Position += ReadSize;
>
Taking Position into account (here and in the Ext4Read call) seems wrong.
Why would the file seek affect the readlink() operation?

> +
> +  //
> +  // Add null-terminator
> +  //
> +  SymlinkTmp[SymlinkSizeTmp] = '\0';
> +
> +  if (SymlinkSizeTmp != ReadSize) {
> +    DEBUG ((
> +      DEBUG_FS,
> +      "[ext4] Error! The sz of the read block doesn't match the value
> from the inode!\n"
>
Nit: size

> +      ));
> +    return EFI_VOLUME_CORRUPTED;
> +  }
> +
> +  *AsciiSymlinkSize = SymlinkAllocateSize;
> +  *AsciiSymlink     = SymlinkTmp;
> +
> +  return EFI_SUCCESS;
> +}
> +
> +/**
> +  Reads a symlink file.
> +
> +  @param[in]      Partition   Pointer to the ext4 partition.
> +  @param[in]      File        Pointer to the open symlink file.
> +  @param[out]     Symlink     Pointer to the output unicode symlink
> string.
> +
> +  @retval EFI_SUCCESS           Symlink was read.
> +  @retval EFI_ACCESS_DENIED     Symlink is encrypted.
> +  @retval EFI_OUT_OF_RESOURCES  Memory allocation error.
> +  @retval EFI_INVALID_PARAMETER Symlink path has incorrect length
> +  @retval EFI_VOLUME_CORRUPTED  Symlink read block size differ from inode
> value
> +**/
> +EFI_STATUS
> +Ext4ReadSymlink (
> +  IN     EXT4_PARTITION  *Partition,
> +  IN     EXT4_FILE       *File,
> +  OUT    CHAR16          **Symlink
> +  )
> +{
> +  EFI_STATUS  Status;
> +  CHAR8       *SymlinkTmp;
> +  UINT32      SymlinkSize;
> +  CHAR16      *Symlink16Tmp;
> +  CHAR16      *Needle;
> +
> +  //
> +  // Assume that we alread read Inode via Ext4ReadInode
> +  // Skip reading, just check encryption flag
> +  //
> +  if ((File->Inode->i_flags & EXT4_ENCRYPT_FL) != 0) {
> +    DEBUG ((DEBUG_FS, "[ext4] Error, symlink is encrypted\n"));
>
Nit: DEBUG_ERROR and "Error: ".

> +    return EFI_ACCESS_DENIED;
> +  }
> +
> +  if (Ext4SymlinkIsFastSymlink (File)) {
> +    Status = Ext4ReadFastSymlink (Partition, File, &SymlinkTmp,
> &SymlinkSize);
> +  } else {
> +    Status = Ext4ReadSlowSymlink (Partition, File, &SymlinkTmp,
> &SymlinkSize);
> +  }
> +
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((DEBUG_FS, "[ext4] Symlink read error with Status %r\n",
> Status));
> +    return Status;
> +  }
> +
> +  Symlink16Tmp = AllocateZeroPool (SymlinkSize * sizeof (CHAR16));
> +  if (Symlink16Tmp == NULL) {
> +    DEBUG ((DEBUG_FS, "[ext4] Failed to allocate symlink unicode string
> buffer\n"));
> +    FreePool (SymlinkTmp);
> +    return EFI_OUT_OF_RESOURCES;
> +  }
> +
> +  Status = AsciiStrToUnicodeStrS (
> +             SymlinkTmp,
> +             Symlink16Tmp,
> +             SymlinkSize
> +             );
> +
> +  if (EFI_ERROR (Status)) {
> +    DEBUG ((
> +      DEBUG_FS,
> +      "[ext4] Failed to convert ascii symlink to unicode with Status
> %r\n",
> +      Status
> +      ));
> +    FreePool (Symlink16Tmp);
> +    FreePool (SymlinkTmp);
> +    return Status;
> +  }
> +
> +  //
> +  // Convert to UEFI slashes
> +  //
> +  for (Needle = Symlink16Tmp; *Needle != L'\0'; Needle++) {
> +    if (*Needle == L'/') {
> +      *Needle = L'\\';
> +    }
> +  }
> +
> +  *Symlink = Symlink16Tmp;
> +
> +  FreePool (SymlinkTmp);
> +  return Status;
> +}
> +
>  /**
>    Opens a new file relative to the source file's location.
>
> -  @param[in]  This       A pointer to the EFI_FILE_PROTOCOL instance that
> is the file
> +  @param[out] FoundFile  A pointer to the location to return the opened
> handle for the new
> +                         file.
> +  @param[in]  Source     A pointer to the EXT4_FILE instance that is the
> file
>                           handle to the source location. This would
> typically be an open
>                           handle to a directory.
> -  @param[out] NewHandle  A pointer to the location to return the opened
> handle for the new
> -                         file.
>    @param[in]  FileName   The Null-terminated string of the name of the
> file to be opened.
>                           The file name may contain the following path
> modifiers: "\", ".",
>                           and "..".
> @@ -165,13 +375,12 @@ Ext4DirCanLookup (
>
>  **/
>  EFI_STATUS
> -EFIAPI
> -Ext4Open (
> -  IN EFI_FILE_PROTOCOL   *This,
> -  OUT EFI_FILE_PROTOCOL  **NewHandle,
> -  IN CHAR16              *FileName,
> -  IN UINT64              OpenMode,
> -  IN UINT64              Attributes
> +Ext4OpenInternal (
> +  OUT EXT4_FILE  **FoundFile,
> +  IN  EXT4_FILE  *Source,
> +  IN  CHAR16     *FileName,
> +  IN  UINT64     OpenMode,
> +  IN  UINT64     Attributes
>    )
>  {
>    EXT4_FILE       *Current;
> @@ -180,13 +389,14 @@ Ext4Open (
>    CHAR16          PathSegment[EXT4_NAME_MAX + 1];
>    UINTN           Length;
>    EXT4_FILE       *File;
> +  CHAR16          *Symlink;
>    EFI_STATUS      Status;
>
> -  Current   = (EXT4_FILE *)This;
> +  Current   = Source;
>    Partition = Current->Partition;
>    Level     = 0;
>
> -  DEBUG ((DEBUG_FS, "[ext4] Ext4Open %s\n", FileName));
> +  DEBUG ((DEBUG_FS, "[ext4] Ext4OpenInternal %s\n", FileName));
>    // If the path starts with a backslash, we treat the root directory as
> the base directory
>    if (FileName[0] == L'\\') {
>      FileName++;
> @@ -194,6 +404,11 @@ Ext4Open (
>    }
>
>    while (FileName[0] != L'\0') {
> +    if (Partition->Root->



> > SYMLOOP_MAX) {
> +      DEBUG ((DEBUG_FS, "[ext4] Symloop limit is hit !\n"));
> +      return EFI_ACCESS_DENIED;
> +    }
> +
>      // Discard leading path separators
>      while (FileName[0] == L'\\') {
>        FileName++;
> @@ -238,18 +453,45 @@ Ext4Open (
>      }
>
>      // Check if this is a valid file to open in EFI
> -
> -    // What to do with symlinks? They're nonsense when absolute but may
> -    // be useful when they're relative. Right now, they're ignored, since
> they
> -    // bring a lot of trouble for something that's not as useful in our
> case.
> -    // If you want to link, use hard links.
> -
>      if (!Ext4FileIsOpenable (File)) {
>        Ext4CloseInternal (File);
>        // This looks like an /okay/ status to return.
>        return EFI_ACCESS_DENIED;
>      }
>
> +    //
> +    // Reading symlink and then trying to follow it
> +    //
> +    if (Ext4FileIsSymlink (File)) {
> +      Partition->Root->SymLoops++;
> +      DEBUG ((DEBUG_FS, "[ext4] File %s is symlink, trying to read it\n",
> PathSegment));
> +      Status = Ext4ReadSymlink (Partition, File, &Symlink);
> +      if (EFI_ERROR (Status)) {
> +        DEBUG ((DEBUG_FS, "[ext4] Error reading %s symlink!\n",
> PathSegment));
> +        return Status;
> +      }
> +
> +      DEBUG ((DEBUG_FS, "[ext4] File %s is linked to %s\n", PathSegment,
> Symlink));
> +      //
> +      // Close symlink file
> +      //
> +      Ext4CloseInternal (File);
> +      //
> +      // Open linked file by recursive call of Ext4OpenFile
> +      //
> +      Status = Ext4OpenInternal (FoundFile, Current, Symlink, OpenMode,
> Attributes);
> +      FreePool (Symlink);
> +      if (EFI_ERROR (Status)) {
> +        DEBUG ((DEBUG_FS, "[ext4] Error opening linked file %s\n",
> Symlink));
> +        return Status;
> +      }
> +
> +      //
> +      // Set File to newly opened
> +      //
> +      File = *FoundFile;
> +    }
> +
>      if (Level != 0) {
>        // Careful not to close the base directory
>        Ext4CloseInternal (Current);
> @@ -273,12 +515,75 @@ Ext4Open (
>      return EFI_ACCESS_DENIED;
>    }
>
> -  *NewHandle = &Current->Protocol;
> +  *FoundFile = Current;
>
>    DEBUG ((DEBUG_FS, "[ext4] Opened filename %s\n",
> Current->Dentry->Name));
>    return EFI_SUCCESS;
>  }
>
> +/**
> +  Opens a new file relative to the source file's location.
> +  @param[in]  This       A pointer to the EFI_FILE_PROTOCOL instance that
> is the file
> +                         handle to the source location. This would
> typically be an open
> +                         handle to a directory.
> +  @param[out] NewHandle  A pointer to the location to return the opened
> handle for the new
> +                         file.
> +  @param[in]  FileName   The Null-terminated string of the name of the
> file to be opened.
> +                         The file name may contain the following path
> modifiers: "\", ".",
> +                         and "..".
> +  @param[in]  OpenMode   The mode to open the file. The only valid
> combinations that the
> +                         file may be opened with are: Read, Read/Write,
> or Create/Read/Write.
> +  @param[in]  Attributes Only valid for EFI_FILE_MODE_CREATE, in which
> case these are the
> +                         attribute bits for the newly created file.
> +  @retval EFI_SUCCESS          The file was opened.
> +  @retval EFI_NOT_FOUND        The specified file could not be found on
> the device.
> +  @retval EFI_NO_MEDIA         The device has no medium.
> +  @retval EFI_MEDIA_CHANGED    The device has a different medium in it or
> the medium is no
> +                               longer supported.
> +  @retval EFI_DEVICE_ERROR     The device reported an error.
> +  @retval EFI_VOLUME_CORRUPTED The file system structures are corrupted.
> +  @retval EFI_WRITE_PROTECTED  An attempt was made to create a file, or
> open a file for write
> +                               when the media is write-protected.
> +  @retval EFI_ACCESS_DENIED    The service denied access to the file.
> +  @retval EFI_OUT_OF_RESOURCES Not enough resources were available to
> open the file.
> +  @retval EFI_VOLUME_FULL      The volume is full.
> +**/
> +EFI_STATUS
> +EFIAPI
> +Ext4Open (
> +  IN EFI_FILE_PROTOCOL   *This,
> +  OUT EFI_FILE_PROTOCOL  **NewHandle,
> +  IN CHAR16              *FileName,
> +  IN UINT64              OpenMode,
> +  IN UINT64              Attributes
> +  )
> +{
> +  EFI_STATUS  Status;
> +  EXT4_FILE   *FoundFile;
> +  EXT4_FILE   *Source;
> +
> +  Source = (EXT4_FILE *)This;
> +
> +  //
> +  // Reset SymLoops counter
> +  //
> +  Source->Partition->Root->SymLoops = 0;
>
Keeping SymLoops in the root FILE seems kind of out of place. My idea here
(and this was going to be chained with a bunch of improvements to the path
walking logic, which is why I never got around to adding symlink support)
was to add a nameidata(see Onyx code, or NetBSD's namei(9) manpage)-like
structure, as you would in typical UNIX fashion. You would then do your
whole path traversal on that structure, which would keep your path walking
state, walked_symlinks, etc.

> +
> +  Status = Ext4OpenInternal (
> +             &FoundFile,
> +             Source,
> +             FileName,
> +             OpenMode,
> +             Attributes
> +             );
> +
> +  if (!EFI_ERROR (Status)) {
> +    *NewHandle = &FoundFile->Protocol;
> +  }
> +
> +  return Status;
> +}
> +
>  /**
>    Closes a specified file handle.
>
> @@ -588,7 +893,7 @@ Ext4GetVolumeName (
>
>    // s_volume_name is only valid on dynamic revision; old filesystems
> don't support this
>    if (Partition->SuperBlock.s_rev_level == EXT4_DYNAMIC_REV) {
> -    CopyMem (TempVolName, (CONST CHAR8
> *)Partition->SuperBlock.s_volume_name, 16);
> +    CopyMem (TempVolName, Partition->SuperBlock.s_volume_name, 16);
>      TempVolName[16] = '\0';
>
>      Status = UTF8StrToUCS2 (TempVolName, &VolumeName);
> @@ -754,12 +1059,14 @@ Ext4GetInfo (
>    OUT VOID              *Buffer
>    )
>  {
> +  EXT4_FILE       *File;
>    EXT4_PARTITION  *Partition;
>
> -  Partition = ((EXT4_FILE *)This)->Partition;
> +  File      = (EXT4_FILE *)This;
> +  Partition = File->Partition;
>
>    if (CompareGuid (InformationType, &gEfiFileInfoGuid)) {
> -    return Ext4GetFileInfo ((EXT4_FILE *)This, Buffer, BufferSize);
> +    return Ext4GetFileInfo (File, Buffer, BufferSize);
>    }
>
>    if (CompareGuid (InformationType, &gEfiFileSystemInfoGuid)) {
> @@ -870,12 +1177,12 @@ Ext4SetInfo (
>    )
>  {
>    EXT4_FILE       *File;
> -  EXT4_PARTITION  *Part;
> +  EXT4_PARTITION  *Partition;
>
> -  File = (EXT4_FILE *)This;
> -  Part = File->Partition;
> +  File      = (EXT4_FILE *)This;
> +  Partition = File->Partition;
>
> -  if (Part->ReadOnly) {
> +  if (Partition->ReadOnly) {
>      return EFI_WRITE_PROTECTED;
>    }
>
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Inode.c
> b/Features/Ext4Pkg/Ext4Dxe/Inode.c
> index 831f5946e870..e7a6b3225709 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Inode.c
> +++ b/Features/Ext4Pkg/Ext4Dxe/Inode.c
> @@ -255,6 +255,59 @@ Ext4FileIsDir (
>    return (File->Inode->i_mode & EXT4_INO_TYPE_DIR) == EXT4_INO_TYPE_DIR;
>  }
>
> +/**
> +   Checks if a file is a symlink.
> +
> +   @param[in]      File          Pointer to the opened file.
> +
> +   @return BOOLEAN         Whether file is a symlink
> +**/
> +BOOLEAN
> +Ext4FileIsSymlink (
> +  IN CONST EXT4_FILE  *File
> +  )
> +{
> +  return (File->Inode->i_mode & EXT4_INO_TYPE_SYMLINK) ==
> EXT4_INO_TYPE_SYMLINK;
> +}
> +
> +/**
> +   Detects if a symlink is a fast symlink.
> +
> +   @param[in]      File          Pointer to the opened file.
> +
> +   @return BOOLEAN         Whether symlink is a fast symlink
> +**/
> +BOOLEAN
> +Ext4SymlinkIsFastSymlink (
> +  IN CONST EXT4_FILE  *File
> +  )
> +{
> +  //
> +  // Detection logic of the fast-symlink splits into two behaviors - old
> and new.
> +  // The old behavior is based on comparing the extended attribute blocks
> +  // with the inode's i_blocks, and if it's zero we know the inode isn't
> storing
> +  // the link in filesystem blocks, so we look to the inode->i_data.
> +  // The new behavior is apparently needed only with the large EA inode
> feature.
> +  // In this case we check that inode size less than maximum fast symlink
> size.
> +  // So, we revert to the old behavior if the large EA inode feature is
> not set.
> +  //
> +  UINT32  FileAcl;
> +  UINT32  ExtAttrBlocks;
> +
> +  if ((File->Inode->i_flags & EXT4_EA_INODE_FL) == 0) {
> +    FileAcl = File->Inode->i_file_acl;
> +    if (EXT4_IS_64_BIT (File->Partition)) {
> +      FileAcl |= LShiftU64
> (File->Inode->i_osd2.data_linux.l_i_file_acl_high, 32);
> +    }
> +
> +    ExtAttrBlocks = FileAcl != 0 ? (File->Partition->BlockSize >> 9) : 0;
> +
> +    return File->Inode->i_blocks == ExtAttrBlocks;
> +  }
> +
> +  return EXT4_INODE_SIZE (File->Inode) <= EXT4_FAST_SYMLINK_MAX_SIZE;
> +}
> +
>  /**
>     Checks if a file is a regular file.
>     @param[in]      File          Pointer to the opened file.
> --
> 2.37.1
>
>

-- 
Pedro Falcato

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