[PATCHv2] cmd/gpt: Address error cases during gpt rename more correctly

[Simon Goldschmidt]

On Mon, Jan 20, 2020 at 11:53 PM Tom Rini <trini at konsulko.com> wrote:
>
> New analysis by the tool has shown that we have some cases where we
> weren't handling the error exit condition correctly.  When we ran into
> the ENOMEM case we wouldn't exit the function and thus incorrect things
> could happen.  Rework the unwinding such that we don't need a helper
> function now and free what we may have allocated.
>
> Fixes: 18030d04d25d ("GPT: fix memory leaks identified by Coverity")
> Reported-by: Coverity (CID: 275475, 275476)
> Cc: Alison Chaiken <alison at she-devel.com>
> Cc: Simon Goldschmidt <simon.k.r.goldschmidt at gmail.com>
> Cc: Jordy <jordy at simplyhacker.com>
> Signed-off-by: Tom Rini <trini at konsulko.com>
>
> ---
> Changes in v2:
> - Initialize str_disk_guid to NULL to be sure we can test that it has
>   been set later on (Simon, Jordy).
>
>  cmd/gpt.c | 37 +++++++++----------------------------
>  1 file changed, 9 insertions(+), 28 deletions(-)
>
> diff --git a/cmd/gpt.c b/cmd/gpt.c
> index 0c4349f4b249..c0e3c5161789 100644
> --- a/cmd/gpt.c
> +++ b/cmd/gpt.c
> @@ -633,21 +633,6 @@ static int do_disk_guid(struct blk_desc *dev_desc, char * const namestr)
>  }
>
>  #ifdef CONFIG_CMD_GPT_RENAME
> -/*
> - * There are 3 malloc() calls in set_gpt_info() and there is no info about which
> - * failed.
> - */
> -static void set_gpt_cleanup(char **str_disk_guid,
> -                           disk_partition_t **partitions)
> -{
> -#ifdef CONFIG_RANDOM_UUID
> -       if (str_disk_guid)
> -               free(str_disk_guid);
> -#endif
> -       if (partitions)
> -               free(partitions);
> -}
> -
>  static int do_rename_gpt_parts(struct blk_desc *dev_desc, char *subcomm,
>                                char *name1, char *name2)
>  {
> @@ -655,7 +640,7 @@ static int do_rename_gpt_parts(struct blk_desc *dev_desc, char *subcomm,
>         struct disk_part *curr;
>         disk_partition_t *new_partitions = NULL;
>         char disk_guid[UUID_STR_LEN + 1];
> -       char *partitions_list, *str_disk_guid;
> +       char *partitions_list, *str_disk_guid = NULL;
>         u8 part_count = 0;
>         int partlistlen, ret, numparts = 0, partnum, i = 1, ctr1 = 0, ctr2 = 0;
>
> @@ -699,11 +684,7 @@ static int do_rename_gpt_parts(struct blk_desc *dev_desc, char *subcomm,
>                            &new_partitions, &part_count);
>         if (ret < 0) {
>                 del_gpt_info();
> -               free(partitions_list);
> -               if (ret == -ENOMEM)
> -                       set_gpt_cleanup(&str_disk_guid, &new_partitions);
> -               else
> -                       goto out;
> +               goto out;
>         }
>
>         if (!strcmp(subcomm, "swap")) {
> @@ -768,11 +749,7 @@ static int do_rename_gpt_parts(struct blk_desc *dev_desc, char *subcomm,
>          */
>         if (ret < 0) {
>                 del_gpt_info();
> -               free(partitions_list);
> -               if (ret == -ENOMEM)
> -                       set_gpt_cleanup(&str_disk_guid, &new_partitions);
> -               else
> -                       goto out;
> +               goto out;
>         }
>
>         debug("Writing new partition table\n");
> @@ -797,8 +774,12 @@ static int do_rename_gpt_parts(struct blk_desc *dev_desc, char *subcomm,
>         print_gpt_info();
>         del_gpt_info();
>   out:

OK, so the freeing below looks good to me now. However, what worries me is that
when reaching 'out:' via different code flows, del_gpt_info is not always
called. I think that could lead to memory leaks when calling this code again, as
get_gpt_info just reinitializes the list head without checking if there's
actually something allocated in the list.

Maybe we should move the last call to del_gpt_info below 'out:' so that it is
always called?

Regards,
Simon

> -       free(new_partitions);
> -       free(str_disk_guid);
> +#ifdef CONFIG_RANDOM_UUID
> +       if (str_disk_guid)
> +               free(str_disk_guid);
> +#endif
> +       if (new_partitions)
> +               free(new_partitions);
>         free(partitions_list);
>         return ret;
>  }
> --
> 2.17.1