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@...>
Cc: Pedro Falcato <pedro.falcato@...>
Cc: Vitaly Cheptsov <vit9696@...>
Signed-off-by: Savva Mitrofanov <savvamtr@...>
---
Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h | 2 +-
Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h | 99 +++++-
Features/Ext4Pkg/Ext4Dxe/File.c | 365 ++++++++++++++++++--
Features/Ext4Pkg/Ext4Dxe/Inode.c | 38 ++
4 files changed, 470 insertions(+), 34 deletions(-)

diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h b/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
index a55cd2fa68ad..6f83dcf65429 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
diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
index b1508482b0a7..a1eb32aa2cff 100644
--- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
+++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
@@ -31,7 +31,10 @@

#include "Ext4Disk.h"

-#define EXT4_NAME_MAX 255
+#define SYMLOOP_MAX 8
+#define EXT4_NAME_MAX 255
+#define EFI_PATH_MAX 4096
+#define EXT4_FAST_SYMLINK_SIZE 60

#define EXT4_DRIVER_VERSION 0x0000

@@ -324,11 +327,11 @@ 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 +371,7 @@ struct _Ext4File {

UINT64 OpenMode;
UINT64 Position;
+ UINT32 Symloops;

EXT4_PARTITION *Partition;

@@ -497,6 +501,45 @@ 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,
+ IN EXT4_FILE *Source,
+ IN CHAR16 *FileName,
+ IN UINT64 OpenMode,
+ IN UINT64 Attributes
+ );
+
/**
Closes a file.

@@ -774,6 +817,28 @@ Ext4FileIsDir (
IN CONST EXT4_FILE *File
);

+/**
+ Checks if a file is a symlink.
+ @param[in] File Pointer to the opened file.
+
+ @return TRUE if 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 TRUE if file is a fast symlink.
+**/
+BOOLEAN
+Ext4SymlinkIsFastSymlink (
+ IN CONST EXT4_FILE *File
+ );
+
/**
Checks if a file is a regular file.
@param[in] File Pointer to the opened file.
@@ -797,7 +862,7 @@ 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 +1000,26 @@ 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..0fb9e05e6647 100644
--- a/Features/Ext4Pkg/Ext4Dxe/File.c
+++ b/Features/Ext4Pkg/Ext4Dxe/File.c
@@ -134,14 +134,230 @@ 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
+ )
+{
+ EFI_STATUS Status;
+ CHAR8 *AsciiSymlinkTmp;
+
+ AsciiSymlinkTmp = AllocatePool (EXT4_FAST_SYMLINK_SIZE + 1);
+ if (AsciiSymlinkTmp == NULL) {
+ Status = EFI_OUT_OF_RESOURCES;
+ DEBUG ((DEBUG_FS, "[ext4] Failed to allocate symlink ascii string buffer\n"));
+ return Status;
+ }
+
+ CopyMem (AsciiSymlinkTmp, File->Inode->i_data, EXT4_FAST_SYMLINK_SIZE);
+
+ //
+ // Add null-terminator
+ //
+ AsciiSymlinkTmp[EXT4_FAST_SYMLINK_SIZE] = '\0';
+
+ *AsciiSymlink = AsciiSymlinkTmp;
+ *AsciiSymlinkSize = EXT4_FAST_SYMLINK_SIZE + 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) {
+ SymlinkAllocateSize = (UINT32)SymlinkSizeTmp + 1;
+ } else {
+ DEBUG ((
+ DEBUG_FS,
+ "[ext4] Error! Symlink path maximum length was hit!\n"
+ ));
+ return EFI_INVALID_PARAMETER;
+ }
+
+ 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)) {
+ File->Position += ReadSize;
+ } else {
+ DEBUG ((DEBUG_FS, "[ext4] Failed to read symlink from blocks with Status %r\n", Status));
+ FreePool (SymlinkTmp);
+ return Status;
+ }
+
+ //
+ // Add null-terminator
+ //
+ SymlinkTmp[SymlinkSizeTmp] = '\0';
+
+ //
+ // It is not clear, should we check that symlink allocation size is
+ // equal symlink string size or not. However there is no checks in existing
+ // Ext4 implementations, so we also don't check it here relying on the fact
+ // we terminated string ourselves above.
+ //
+ // ASSERT (SymlinkAllocateSize == AsciiStrSize (SymlinkTmp));
+ //
+
+ if (SymlinkSizeTmp != ReadSize) {
+ DEBUG ((
+ DEBUG_FS,
+ "[ext4] Error! The sz of the read block doesn't match the value from the inode!\n"
+ ));
+ 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) {
+ Status = EFI_ACCESS_DENIED;
+ DEBUG ((DEBUG_FS, "[ext4] Error, symlink is encrypted\n"));
+ return Status;
+ }
+
+ 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) {
+ Status = EFI_OUT_OF_RESOURCES;
+ DEBUG ((DEBUG_FS, "[ext4] Failed to allocate symlink unicode string buffer\n"));
+ FreePool (SymlinkTmp);
+ return Status;
+ }
+
+ 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
+ //
+ Needle = Symlink16Tmp;
+ while ((Needle = StrStr (Needle, L"/")) != NULL) {
+ *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 +381,12 @@ 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 +395,14 @@ 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 +410,11 @@ Ext4Open (
}

while (FileName[0] != L'\0') {
+ if (Partition->Root->Symloops > 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 +459,45 @@ 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 +521,75 @@ 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;
+
+ Status = Ext4OpenInternal (
+ &FoundFile,
+ Source,
+ FileName,
+ OpenMode,
+ Attributes
+ );
+
+ if (!EFI_ERROR (Status)) {
+ *NewHandle = &FoundFile->Protocol;
+ }
+
+ return Status;
+}
+
/**
Closes a specified file handle.

@@ -588,7 +899,7 @@ 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 +1065,14 @@ 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 +1183,12 @@ 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..e95299c3aee0 100644
--- a/Features/Ext4Pkg/Ext4Dxe/Inode.c
+++ b/Features/Ext4Pkg/Ext4Dxe/Inode.c
@@ -255,6 +255,44 @@ 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 TRUE if 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 TRUE if file is a fast symlink.
+**/
+BOOLEAN
+Ext4SymlinkIsFastSymlink (
+ IN CONST EXT4_FILE *File
+ )
+{
+ //
+ // REF: https://github.com/heatd/Onyx/blob/master/kernel/kernel/fs/ext2/symlink.cpp#L26
+ // Essentially, we're 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 ext2_inode->i_data.
+ //
+ INTN ExtAttrBlocks = File->Inode->i_file_acl ? (File->Partition->BlockSize >> 9) : 0;
+
+ return ( File->Inode->i_blocks == ExtAttrBlocks
+ && EXT4_INODE_SIZE (File->Inode) <= 60
+ );
+}
+
/**
Checks if a file is a regular file.
@param[in] File Pointer to the opened file.
--
2.37.0