Re: [PATCH 1/3] efi/libstub: fix efi_parse_options() ignoring the default command line

[Jonathan Marek]

On 10/12/24 3:46 AM, Ard Biesheuvel wrote:
> Hi Jonathan,
>
> Please use a cover letter when sending more than a single patch.
>
> On Sat, 12 Oct 2024 at 00:51, Jonathan Marek <jonathan@xxxxxxxx> wrote:
> > efi_convert_cmdline() always returns a size of at least 1 because it counts
> > the NUL terminator, so the "cmdline_size == 0" condition is not possible.
> >
> > Change it to compare against 1 to get the intended behavior: to use
> > CONFIG_CMDLINE when load_options_size is 0.
> >
> > Fixes: 60f38de7a8d4 ("efi/libstub: Unify command line param parsing")
> > Signed-off-by: Jonathan Marek <jonathan@xxxxxxxx>
> > ---
> >   drivers/firmware/efi/libstub/efi-stub.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/firmware/efi/libstub/efi-stub.c b/drivers/firmware/efi/libstub/efi-stub.c
> > index 958a680e0660d..709ae2d41a632 100644
> > --- a/drivers/firmware/efi/libstub/efi-stub.c
> > +++ b/drivers/firmware/efi/libstub/efi-stub.c
> > @@ -129,7 +129,7 @@ efi_status_t efi_handle_cmdline(efi_loaded_image_t *image, char **cmdline_ptr)
> >
> >          if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
> >              IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
> > -           cmdline_size == 0) {
> > +           cmdline_size == 1) {
>
> I'd prefer it if we could keep the weirdness local to
> efi_convert_cmdline(). Would the below fix things too?
>
> --- a/drivers/firmware/efi/libstub/efi-stub-helper.c
> +++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
> @@ -395,9 +395,7 @@
>                  }
>          }
>
> -       options_bytes++;        /* NUL termination */
> -
> -       status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, options_bytes,
> +       status = efi_bs_call(allocate_pool, EFI_LOADER_DATA, options_bytes + 1,
>                               (void **)&cmdline_addr);
>          if (status != EFI_SUCCESS)
>                  return NULL;
>
> Note that the only other caller of efi_convert_cmdline() in x86-stub.c
> ignores this value entirely.

Just changing this would just make things more broken, the following 
snprintf would remove the last character of the command line because it 
uses options_bytes.

Since this patch has a Fixes: tag, I wanted to make the fix as simple as 
possible. If you think comparing the size to 1 is "weird", the fix could 
instead check if cmdline[0] is non-NUL (or just strlen(cmdline)==0 if 
you don't like that either).

And then my followup cleanup patch can just remove the cmd_line_len 
argument from efi_convert_cmdline().