On Fri, Jan 27, 2023 at 9:29 AM Savva Mitrofanov <savva...@gmail.com> wrote:
>
> We need to validate inode number to prevent possible null-pointer
> dereference of directory parent in Ext4OpenDirent. Also checks that
> inode number valid across opened partition before we read it in
> Ext4ReadInode.
>
> Cc: Marvin Häuser <mhaeu...@posteo.de>
> Cc: Pedro Falcato <pedro.falc...@gmail.com>
> Cc: Vitaly Cheptsov <vit9...@protonmail.com>
> Fixes: d9ceedca6c8f ("Ext4Pkg: Add Ext4Dxe driver.")
> Signed-off-by: Savva Mitrofanov <savva...@gmail.com>
> ---
> Features/Ext4Pkg/Ext4Dxe/Ext4Disk.h | 13 ++++++++--
> Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h | 25 ++++++++++++++++++++
> Features/Ext4Pkg/Ext4Dxe/BlockGroup.c | 5 ++++
> Features/Ext4Pkg/Ext4Dxe/Directory.c | 10 ++++++++
> 4 files changed, 51 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..2e489ce4dd86 100644
> --- a/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> +++ b/Features/Ext4Pkg/Ext4Dxe/Ext4Dxe.h
> @@ -287,6 +287,31 @@ Ext4GetBlockGroupDesc (
> IN UINT32 BlockGroup
> );
>
> +/**
> + Retrieves the first usable non-reserved inode number from the superblock
> + of the opened partition.
> +
> + @param[in] Partition Pointer to the opened ext4 partition.
> +
> + @return The first usable inode number (non-reserved).
> +**/
> +#define EXT4_FIRST_INODE_NR(Partition)
> \
> + ((Partition->SuperBlock.s_rev_level == EXT4_GOOD_OLD_REV) ?
> \
> + EXT4_GOOD_OLD_FIRST_INODE_NR :
> \
> + Partition->SuperBlock.s_first_ino)
> +
> +/**
> + Checks inode number validity across superblock of the opened partition.
> +
> + @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 == EXT4_ROOT_INODE_NR ||
> \
> + (InodeNum >= EXT4_FIRST_INODE_NR(Partition) &&
> \
> + 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;
> + }
> +
I don't know how to feel about this patch.
I do not understand why we need this here (and below). Given
Ext4OpenDirent, how is this deref'ing a NULL pointer without this
check?
Has this been handled by the UTF8 patches and your \0 patch?
--
Pedro
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