Hi,
On Wed, 14 Dec 2022 18:55:04 +0000 Lidong Chen <[email protected]> wrote:
> Added a check for the SP entry data boundary before reading it.
>
> Signed-off-by: Lidong Chen <[email protected]>
> ---
> grub-core/fs/iso9660.c | 16 ++++++++++++++--
> 1 file changed, 14 insertions(+), 2 deletions(-)
>
> diff --git a/grub-core/fs/iso9660.c b/grub-core/fs/iso9660.c
> index 9170fa820..67aa8451c 100644
> --- a/grub-core/fs/iso9660.c
> +++ b/grub-core/fs/iso9660.c
> @@ -408,6 +408,9 @@ set_rockridge (struct grub_iso9660_data *data)
> if (!sua_size)
> return GRUB_ERR_NONE;
>
> + if (sua_size < GRUB_ISO9660_SUSP_HEADER_SZ)
As mentioned in my review of patch [2/4], GRUB_ISO9660_SUSP_HEADER_SZ should
be defined as 4, rather than as 5. Else entry RE could trigger this error:
> + return grub_error (GRUB_ERR_BAD_FS, "invalid rock ridge entry size");
> +
> sua = grub_malloc (sua_size);
> if (! sua)
> return grub_errno;
> @@ -434,8 +437,17 @@ set_rockridge (struct grub_iso9660_data *data)
> rootnode.have_symlink = 0;
> rootnode.dirents[0] = data->voldesc.rootdir;
>
> - /* The 2nd data byte stored how many bytes are skipped every time
> - to get to the SUA (System Usage Area). */
> + /*
> + * The 2nd data byte stored how many bytes are skipped every time
> + * to get to the SUA (System Usage Area).
> + */
> + if (sua_size < GRUB_ISO9660_SUSP_HEADER_SZ + 2 ||
> + entry->len < GRUB_ISO9660_SUSP_HEADER_SZ + 2)
This interprets an SP entry, which is specified to have 7 bytes.
So if GRUB_ISO9660_SUSP_HEADER_SZ gets corrected to 4, then the size demand
will have to be (GRUB_ISO9660_SUSP_HEADER_SZ + 3).
Like with the NM interpretation i would rather prefer a plain "7", maybe with
a comment which says that this is the fixed size of SP (version 1).
> + {
> + grub_free (sua);
> + return grub_error (GRUB_ERR_BAD_FS, "corrupted rock ridge entry");
> + }
> +
> data->susp_skip = entry->data[2];
> entry = (struct grub_iso9660_susp_entry *) ((char *) entry +
> entry->len);
>
> --
> 2.35.1
>
Reviewed-by: Thomas Schmitt <[email protected]>
But the expression (GRUB_ISO9660_SUSP_HEADER_SZ + 2) will need correction if
my wish for
#define GRUB_ISO9660_SUSP_HEADER_SZ 4
gets fulfilled. As said, i'd prefer a plain "7".
Have a nice day :)
Thomas
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