Re: [PATCH v2 1/1] fs/udf: Fix out of bounds access

[Darren Kenny <darren.kenny@oracle.com>]

Hi Li,,

LGTM!

Reviewed-by: Darren Kenny <darren.kenny@oracle.com>

Thanks,

Darren.

On Wednesday, 2023-06-07 at 01:31:06 UTC, Lidong Chen wrote:
> Implemented a boundary check before advancing the allocation
> descriptors pointer.
>
> Signed-off-by: Lidong Chen <lidong.chen@oracle.com>
> Reviewed-by: Darren Kenny <darren.kenny@oracle.com>
> Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
> ---
>  grub-core/fs/udf.c | 38 ++++++++++++++++++++++++++++++++++++++
>  1 file changed, 38 insertions(+)
>
> diff --git a/grub-core/fs/udf.c b/grub-core/fs/udf.c
> index 7679ea309..58884d2ba 100644
> --- a/grub-core/fs/udf.c
> +++ b/grub-core/fs/udf.c
> @@ -114,6 +114,10 @@ GRUB_MOD_LICENSE ("GPLv3+");
>  #define GRUB_UDF_PARTMAP_TYPE_1		1
>  #define GRUB_UDF_PARTMAP_TYPE_2		2
>  
> +#define GRUB_UDF_INVALID_STRUCT_PTR(_ptr, _struct)	\
> +  ((char *) (_ptr) >= end_ptr || \
> +   ((grub_ssize_t)(end_ptr - (char*)(_ptr)) < (grub_ssize_t)sizeof(_struct)))
> +
>  struct grub_udf_lb_addr
>  {
>    grub_uint32_t block_num;
> @@ -458,6 +462,7 @@ grub_udf_read_block (grub_fshelp_node_t node, grub_disk_addr_t fileblock)
>    char *ptr;
>    grub_ssize_t len;
>    grub_disk_addr_t filebytes;
> +  char *end_ptr;
>  
>    switch (U16 (node->block.fe.tag.tag_ident))
>      {
> @@ -476,9 +481,17 @@ grub_udf_read_block (grub_fshelp_node_t node, grub_disk_addr_t fileblock)
>        return 0;
>      }
>  
> +  end_ptr = (char *) node + get_fshelp_size (node->data);
> +
>    if ((U16 (node->block.fe.icbtag.flags) & GRUB_UDF_ICBTAG_FLAG_AD_MASK)
>        == GRUB_UDF_ICBTAG_FLAG_AD_SHORT)
>      {
> +      if (GRUB_UDF_INVALID_STRUCT_PTR(ptr, struct grub_udf_short_ad))
> +	{
> +	  grub_error (GRUB_ERR_BAD_FS, "corrupted UDF file system");
> +	  return 0;
> +	}
> +
>        struct grub_udf_short_ad *ad = (struct grub_udf_short_ad *) ptr;
>  
>        filebytes = fileblock * U32 (node->data->lvd.bsize);
> @@ -542,10 +555,22 @@ grub_udf_read_block (grub_fshelp_node_t node, grub_disk_addr_t fileblock)
>  	  filebytes -= adlen;
>  	  ad++;
>  	  len -= sizeof (struct grub_udf_short_ad);
> +
> +	  if (GRUB_UDF_INVALID_STRUCT_PTR(ad, struct grub_udf_short_ad))
> +	    {
> +	      grub_error (GRUB_ERR_BAD_FS, "corrupted UDF file system");
> +	      return 0;
> +	    }
>  	}
>      }
>    else
>      {
> +      if (GRUB_UDF_INVALID_STRUCT_PTR(ptr, struct grub_udf_long_ad))
> +	{
> +	  grub_error (GRUB_ERR_BAD_FS, "corrupted UDF file system");
> +	  return 0;
> +	}
> +
>        struct grub_udf_long_ad *ad = (struct grub_udf_long_ad *) ptr;
>  
>        filebytes = fileblock * U32 (node->data->lvd.bsize);
> @@ -611,6 +636,12 @@ grub_udf_read_block (grub_fshelp_node_t node, grub_disk_addr_t fileblock)
>  	  filebytes -= adlen;
>  	  ad++;
>  	  len -= sizeof (struct grub_udf_long_ad);
> +
> +	  if (GRUB_UDF_INVALID_STRUCT_PTR(ad, struct grub_udf_long_ad))
> +	    {
> +	      grub_error (GRUB_ERR_BAD_FS, "corrupted UDF file system");
> +	      return 0;
> +	    }
>  	}
>      }
>  
> @@ -630,6 +661,7 @@ grub_udf_read_file (grub_fshelp_node_t node,
>      case GRUB_UDF_ICBTAG_FLAG_AD_IN_ICB:
>        {
>  	char *ptr;
> +	char *end_ptr = (char *) node + get_fshelp_size (node->data);
>  
>  	ptr = ((U16 (node->block.fe.tag.tag_ident) == GRUB_UDF_TAG_IDENT_FE) ?
>  	       ((char *) &node->block.fe.ext_attr[0]
> @@ -637,6 +669,12 @@ grub_udf_read_file (grub_fshelp_node_t node,
>  	       ((char *) &node->block.efe.ext_attr[0]
>                  + U32 (node->block.efe.ext_attr_length)));
>  
> +	if ((ptr + pos + len) > end_ptr)
> +	  {
> +	    grub_error (GRUB_ERR_BAD_FS, "corrupted UDF file system");
> +	    return 0;
> +	  }
> +
>  	grub_memcpy (buf, ptr + pos, len);
>  
>  	return len;
> -- 
> 2.39.1