Re: [edk2-platforms][PATCH v4 04/12] Ext4Pkg: Add inode number validity check

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

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

> On 2. Feb 2023, at 11:21, Savva Mitrofanov <savvamtr@gmail.com> wrote:
> 
> We need to validate inode number to prevent reading non-existent and
> incorrect inodes so we checks that inode number valid across opened
> partition before we read it in Ext4ReadInode.
> 
> Cc: Marvin Häuser <mhaeuser@posteo.de>
> Cc: Pedro Falcato <pedro.falcato@gmail.com>
> Cc: Vitaly Cheptsov <vit9696@protonmail.com>
> Fixes: d9ceedca6c8f ("Ext4Pkg: Add Ext4Dxe driver.")
> Signed-off-by: Savva Mitrofanov <savvamtr@gmail.com>
> ---
> Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h   | 13 +++++++++++--
> Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h    | 12 ++++++++++++
> Features/Ext4Pkg/Ext4Dxe/BlockGroup.c |  5 +++++
> 3 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h b/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> index d0a455d0e572..70cb6c3209dd 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h
> @@ -484,8 +484,17 @@ typedef UINT64  EXT4_BLOCK_NR;
> typedef UINT32  EXT2_BLOCK_NR;
> typedef UINT32  EXT4_INO_NR;
> 
> -// 2 is always the root inode number in ext4
> -#define EXT4_ROOT_INODE_NR  2
> +/* Special inode numbers */
> +#define EXT4_ROOT_INODE_NR         2
> +#define EXT4_USR_QUOTA_INODE_NR    3
> +#define EXT4_GRP_QUOTA_INODE_NR    4
> +#define EXT4_BOOT_LOADER_INODE_NR  5
> +#define EXT4_UNDEL_DIR_INODE_NR    6
> +#define EXT4_RESIZE_INODE_NR       7
> +#define EXT4_JOURNAL_INODE_NR      8
> +
> +/* First non-reserved inode for old ext4 filesystems */
> +#define EXT4_GOOD_OLD_FIRST_INODE_NR  11
> 
> #define EXT4_BLOCK_FILE_HOLE  0
> 
> diff --git a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> index f608def7c9eb..c977a97ca5c2 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> @@ -287,6 +287,18 @@ Ext4GetBlockGroupDesc (
>   IN UINT32          BlockGroup
>   );
> 
> +/**
> +   Checks inode number validity across superblock of the opened partition.
> +   Currently we don't have logic to process defective blocks with
> +   inode number equal 1, so we don't reject them at this point
> +
> +   @param[in]  Partition      Pointer to the opened ext4 partition.
> +
> +   @return TRUE if inode number is valid.
> +**/
> +#define EXT4_IS_VALID_INODE_NR(Partition, InodeNum)                            \
> +  (((InodeNum) > 0) && (InodeNum) <= (Partition->SuperBlock.s_inodes_count))
> +
> /**
>    Reads an inode from disk.
> 
> diff --git a/Features/Ext4Pkg/Ext4Dxe/BlockGroup.c b/Features/Ext4Pkg/Ext4Dxe/BlockGroup.c
> index cba96cd95afc..f34cdc5dbad7 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/BlockGroup.c
> +++ b/Features/Ext4Pkg/Ext4Dxe/BlockGroup.c
> @@ -50,6 +50,11 @@ Ext4ReadInode (
>   EXT4_BLOCK_NR          InodeTableStart;
>   EFI_STATUS             Status;
> 
> +  if (!EXT4_IS_VALID_INODE_NR (Partition, InodeNum)) {
> +    DEBUG ((DEBUG_ERROR, "[ext4] Error reading inode: inode number %lu isn't valid\n", InodeNum));
> +    return EFI_VOLUME_CORRUPTED;
> +  }
> +
>   BlockGroupNumber = (UINT32)DivU64x64Remainder (
>                                InodeNum - 1,
>                                Partition->SuperBlock.s_inodes_per_group,
> -- 
> 2.39.1
>