[PATCH v2 3/4] cmd: gpt: fix calc_parts_list_len()
Simon Glass
sjg at chromium.org
Mon Sep 4 18:48:54 CEST 2023
Hi Heinrich,
On Sat, 2 Sept 2023 at 01:34, Heinrich Schuchardt
<heinrich.schuchardt at canonical.com> wrote:
>
> * Avoid incrementing by moving comma into strlen("uuid_disk=,") and
> considering NUL byte.
> * Appending a UUID only adds UUID_STR_LEN bytes.
> Don't count the terminating NUL.
> * The length of the hexadecimal representation of lba_int is
> 2 * sizeof(lba_int).
> * We don't use a 'MiB' postfix but a '0x' prefix.
Why do we want the 0x prefix?
> * The uuid field is only needed if configured.
>
> Fixes: 2fcaa413b3f6 ("gpt: harden set_gpt_info() against non NULL-terminated strings")
> Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt at canonical.com>
> ---
> v2:
> new patch
> ---
> cmd/gpt.c | 33 ++++++++++++++++++++-------------
> 1 file changed, 20 insertions(+), 13 deletions(-)
>
> diff --git a/cmd/gpt.c b/cmd/gpt.c
> index 092f7defff..e7a53747fc 100644
> --- a/cmd/gpt.c
> +++ b/cmd/gpt.c
> @@ -162,22 +162,29 @@ static bool found_key(const char *str, const char *key)
> return result;
> }
>
> +/**
> + * calc_parts_list_len() - get size of partition table description
> + *
> + * @numparts: number of partitions
> + * Return: string size including terminating NUL
> + */
> static int calc_parts_list_len(int numparts)
> {
> - int partlistlen = UUID_STR_LEN + 1 + strlen("uuid_disk=");
> - /* for the comma */
> - partlistlen++;
> -
> - /* per-partition additions; numparts starts at 1, so this should be correct */
> - partlistlen += numparts * (strlen("name=,") + PART_NAME_LEN + 1);
> + /* number of hexadecimal digits of the lbaint_t representation */
> + const int lbaint_size = 2 * sizeof(lbaint_t);
> + int partlistlen;
> +
> + /* media description including terminating NUL */
> + partlistlen = strlen("uuid_disk=;") + UUID_STR_LEN + 1;
> + /* per-partition descriptions; numparts */
> + partlistlen += numparts * (strlen("name=,") + PART_NAME_LEN);
> /* see part.h for definition of struct disk_partition */
> - partlistlen += numparts * (strlen("start=MiB,") + sizeof(lbaint_t) + 1);
> - partlistlen += numparts * (strlen("size=MiB,") + sizeof(lbaint_t) + 1);
> - partlistlen += numparts * (strlen("uuid=;") + UUID_STR_LEN + 1);
> - /* for the terminating null */
> - partlistlen++;
> - debug("Length of partitions_list is %d for %d partitions\n", partlistlen,
> - numparts);
> + partlistlen += numparts * (strlen("start=0x,") + lbaint_size);
> + partlistlen += numparts * (strlen("size=0x,") + lbaint_size);
> + if (IS_ENABLED(CONFIG_PARTITION_UUIDS))
> + partlistlen += numparts * (strlen("uuid=;") + UUID_STR_LEN);
> + debug("Length of partitions_list is %d for %d partitions\n",
> + partlistlen, numparts);
> return partlistlen;
> }
>
> --
> 2.40.1
>
Regards,
Simon
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