Re: [PATCH 3/3] Ext4Pkg: Fix and clarify handling regarding non-utf8 dir entries

["Marvin Häuser" <mhaeuser@posteo.de>]

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Reviewed-by: Marvin Häuser <mhaeuser@posteo.de <mailto:mhaeuser@posteo.de>>

> On 12. Jan 2023, at 00:59, Pedro Falcato <pedro.falcato@gmail.com> wrote:
> 
> Previously, the handling was mixed and/or non-existent regarding non utf-8
> dirent names. Clarify it.
> 
> Signed-off-by: Pedro Falcato <pedro.falcato@gmail.com>
> Cc: Marvin Häuser <mhaeuser@posteo.de>
> ---
> Features/Ext4Pkg/Ext4Dxe/Directory.c | 37 ++++++++++++++++++++++------
> Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h   |  8 +++---
> 2 files changed, 34 insertions(+), 11 deletions(-)
> 
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Directory.c b/Features/Ext4Pkg/Ext4Dxe/Directory.c
> index 6ed664fc632f..ba781bad968c 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Directory.c
> +++ b/Features/Ext4Pkg/Ext4Dxe/Directory.c
> @@ -1,7 +1,7 @@
> /** @file
>   Directory related routines
> 
> -  Copyright (c) 2021 Pedro Falcato All rights reserved.
> +  Copyright (c) 2021 - 2023 Pedro Falcato All rights reserved.
> 
>   SPDX-License-Identifier: BSD-2-Clause-Patent
> **/
> @@ -16,8 +16,9 @@
>    @param[in]      Entry   Pointer to a EXT4_DIR_ENTRY.
>    @param[out]      Ucs2FileName   Pointer to an array of CHAR16's, of size EXT4_NAME_MAX + 1.
> 
> -   @retval EFI_SUCCESS   The filename was succesfully retrieved and converted to UCS2.
> -   @retval !EFI_SUCCESS  Failure.
> +   @retval EFI_SUCCESS              The filename was succesfully retrieved and converted to UCS2.
> +   @retval EFI_INVALID_PARAMETER    The filename is not valid UTF-8.
> +   @retval !EFI_SUCCESS             Failure.
> **/
> EFI_STATUS
> Ext4GetUcs2DirentName (
> @@ -174,10 +175,16 @@ Ext4RetrieveDirent (
>        * need to form valid ASCII/UTF-8 sequences.
>        */
>       if (EFI_ERROR (Status)) {
> -        // If we error out, skip this entry
> -        // I'm not sure if this is correct behaviour, but I don't think there's a precedent here.
> -        BlockOffset += Entry->rec_len;
> -        continue;
> +        if (Status == EFI_INVALID_PARAMETER) {
> +          // If we error out due to a bad UTF-8 sequence (see Ext4GetUcs2DirentName), skip this entry.
> +          // I'm not sure if this is correct behaviour, but I don't think there's a precedent here.
> +          BlockOffset += Entry->rec_len;
> +          continue;
> +        }
> +
> +        // Other sorts of errors should just error out.
> +        FreePool (Buf);
> +        return Status;
>       }
> 
>       if ((Entry->name_len == StrLen (Name)) &&
> @@ -436,6 +443,7 @@ Ext4ReadDir (
>   EXT4_FILE       *TempFile;
>   BOOLEAN         ShouldSkip;
>   BOOLEAN         IsDotOrDotDot;
> +  CHAR16          DirentUcs2Name[EXT4_NAME_MAX + 1];
> 
>   DirIno     = File->Inode;
>   Status     = EFI_SUCCESS;
> @@ -505,6 +513,21 @@ Ext4ReadDir (
>       continue;
>     }
> 
> +    // Test if the dirent is valid utf-8. This is already done inside Ext4OpenDirent but EFI_INVALID_PARAMETER
> +    // has the danger of its meaning being overloaded in many places, so we can't skip according to that.
> +    // So test outside of it, explicitly.
> +    Status = Ext4GetUcs2DirentName (&Entry, DirentUcs2Name);
> +
> +    if (EFI_ERROR (Status)) {
> +      if (Status == EFI_INVALID_PARAMETER) {
> +        // Bad UTF-8, skip.
> +        Offset += Entry.rec_len;
> +        continue;
> +      }
> +
> +      goto Out;
> +    }
> +
>     Status = Ext4OpenDirent (Partition, EFI_FILE_MODE_READ, &TempFile, &Entry, File);
> 
>     if (EFI_ERROR (Status)) {
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> index 466e49523030..41779dad855f 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> @@ -944,11 +944,11 @@ Ext4StrCmpInsensitive (
>    Retrieves the filename of the directory entry and converts it to UTF-16/UCS-2
> 
>    @param[in]      Entry   Pointer to a EXT4_DIR_ENTRY.
> -   @param[out]      Ucs2FileName   Pointer to an array of CHAR16's, of size
> -EXT4_NAME_MAX + 1.
> +   @param[out]      Ucs2FileName   Pointer to an array of CHAR16's, of size EXT4_NAME_MAX + 1.
> 
> -   @retval EFI_SUCCESS   Unicode collation was successfully initialised.
> -   @retval !EFI_SUCCESS  Failure.
> +   @retval EFI_SUCCESS              The filename was succesfully retrieved and converted to UCS2.
> +   @retval EFI_INVALID_PARAMETER    The filename is not valid UTF-8.
> +   @retval !EFI_SUCCESS             Failure.
> **/
> EFI_STATUS
> Ext4GetUcs2DirentName (
> -- 
> 2.39.0
> 


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