Re: [PATCH] [BUILTIN] describe_command: fix incorrect path

[Youfu Zhang <zhangyoufu@gmail.com>]

Your patch looks better than mine :)

Please consider post this patch to busybox as well.
Their ash has same code and same issue.

See http://lists.busybox.net/pipermail/busybox/2017-May/085459.html

On Fri, May 26, 2017 at 3:59 PM, Harald van Dijk <harald@gigawatt.nl> wrote:
> Hi,
>
> On 26/05/17 09:04, Youfu Zhang wrote:
>>
>> $ PATH=/extra/path:/usr/sbin:/usr/bin:/sbin:/bin \
>>>
>>> sh -xc 'command -V ls; command -V ls; command -Vp ls; command -vp ls'
>>
>> + command -V ls
>> ls is /bin/ls
>> + command -V ls
>> ls is a tracked alias for /bin/ls
>> + command -Vp ls
>> ls is a tracked alias for (null)
>> + command -vp ls
>> Segmentation fault (core dumped)
>>
>> describe_command should respect `path' argument. Looking up in the hash
>> table
>> may gives incorrect index in entry.u.index and finally causes incorrect
>> output
>> or SIGSEGV.
>
>
> True, but only when a path is passed in. If the default path is used,
> looking up in the hash table is correct, and printing tracked aliases is
> intentional.
>
> If it's desirable to drop that feature, then it should be dropped
> completely, code shouldn't be left in that can no longer be used. But it's
> possible to keep it working: how about this instead?
>
> Signed-off-by: Harald van Dijk <harald@gigawatt.nl>
> ---
>  src/exec.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> diff --git a/src/exec.c b/src/exec.c
> index ec0eadd..1350da3 100644
> --- a/src/exec.c
> +++ b/src/exec.c
> @@ -743,8 +743,6 @@ describe_command(out, command, path, verbose)
>         struct tblentry *cmdp;
>         const struct alias *ap;
>
> -       path = path ?: pathval();
> -
>         if (verbose) {
>                 outstr(command, out);
>         }
> @@ -767,8 +765,15 @@ describe_command(out, command, path, verbose)
>                 goto out;
>         }
>
> -       /* Then check if it is a tracked alias */
> -       if ((cmdp = cmdlookup(command, 0)) != NULL) {
> +       /* Then if the standard search path is used, check if it is a
> tracked alias.  */
> +       if (path == NULL) {
> +               path = pathval();
> +               cmdp = cmdlookup(command, 0);
> +       } else {
> +               cmdp = NULL;
> +       }
> +
> +       if (cmdp != NULL) {
>                 entry.cmdtype = cmdp->cmdtype;
>                 entry.u = cmdp->param;
>         } else {