Hi Li,
In general looks good...
On Thursday, 2023-06-01 at 18:50:19 UTC, Lidong Chen wrote:
> Implemented a boundary check before advancing the allocation
> descriptors pointer.
>
> Signed-off-by: Lidong Chen <lidong.c...@oracle.com>
> ---
> grub-core/fs/udf.c | 36 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 36 insertions(+)
>
> diff --git a/grub-core/fs/udf.c b/grub-core/fs/udf.c
> index 12e88ab62..2359222eb 100644
> --- a/grub-core/fs/udf.c
> +++ b/grub-core/fs/udf.c
> @@ -458,6 +458,7 @@ 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 +477,17 @@ 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 ((end_ptr - ptr) < (grub_ssize_t) sizeof (struct grub_udf_short_ad))
>
Should this probably also be testing ptr < end_ptr?
I wonder if a local macro like this would be useful:
#define GRUB_UDF_INVALID_STRUCT_PTR(_ptr, _struct) \
((char *) (_ptr) >= end_ptr ||
((grub_ssize_t)(end_ptr - (char*)(_ptr)) < (grub_ssize_t)sizeof(_struct))
or the more positive and succinct version, and subsequent negated (!) test:
#define GRUB_UDF_VALID_STRUCT_PTR(_ptr, _struct) \
((char *)(_ptr) <= (end_ptr - sizeof(_struct)))
> + {
> + 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);
> @@ -528,10 +537,23 @@ 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 ((char *) ad >= end_ptr ||
> + (end_ptr - (char *) ad) < (grub_ssize_t) sizeof (struct
> grub_udf_short_ad))
> + {
> + grub_error (GRUB_ERR_BAD_FS, "corrupted UDF file system");
> + return 0;
> + }
> }
> }
> else
> {
> + if ((end_ptr - ptr) < (grub_ssize_t) sizeof (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);
> @@ -583,6 +605,13 @@ 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 ((char *) ad >= end_ptr ||
> + (end_ptr - (char *) ad) < (grub_ssize_t) sizeof (struct
> grub_udf_long_ad))
> + {
> + grub_error (GRUB_ERR_BAD_FS, "corrupted UDF file system");
> + return 0;
> + }
> }
> }
>
> @@ -602,6 +631,7 @@ 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]
> @@ -609,6 +639,12 @@ 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 > end_ptr || (ptr + pos) > end_ptr || (ptr + pos + len) >
> end_ptr)
>
Not sure there is a need for all of these, would the last one not
suffice? Might be worth testing that pos and len are > 0 if only using
that one.
Thanks,
Darren.
> + {
> + grub_error (GRUB_ERR_BAD_FS, "corrupted UDF file system");
> + return 0;
> + }
> +
> grub_memcpy (buf, ptr + pos, len);
>
> return len;
> --
> 2.39.1
>
>
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> https://lists.gnu.org/mailman/listinfo/grub-devel
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