Re: [PATCH] blsuki: Fix grub_errno leakage in blsuki_is_default_entry()

On Mon, Nov 10, 2025 at 05:26:02PM +0000, Alec Brown wrote:
> On Mon, Nov 10, 2025 at 2:38 AM, Michael Chang <[email protected]> wrote:
> > The grub_strtol() call in blsuki_is_default_entry() can set grub_errno
> > to GRUB_ERR_BAD_NUMBER if the input string cannot be converted into any
> > valid digits.
> > 
> > This errno value is currently left uncleared, which can lead to
> > unexpected behavior in subsequent logic that tests the result of a
> > function by checking grub_errno.
> > 
> > Clear grub_errno and return false when GRUB_ERR_BAD_NUMBER is set, as
> > this specific error should be ignored in this context.
> 
> grub_strtol() can also set grub_errno to GRUB_ERR_OUT_OF_RANGE. Would it make
> sense to check for that as well? We do return false if def_idx is negative
> or larger than GRUB_INT_MAX, but I don't know if we would want to sustain
> GRUB_ERR_OUT_OF_RANGE in grub_errno past this function should the "def_entry"
> passed into this function contain a bad value that causes grub_strtol() to give
> an error.

Yes, you are right that GRUB_ERR_OUT_OF_RANGE could pass through the
function and cause the same issue as leaked grub_errno. I'll add a check
for this case in the next version.

Thanks,
Michael

> 
> Alec Brown
> 
> > 
> > Signed-off-by: Michael Chang <[email protected]>
> > ---
> >  grub-core/commands/blsuki.c | 6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/grub-core/commands/blsuki.c b/grub-core/commands/blsuki.c
> > index 21d767f05..df25b6fbc 100644
> > --- a/grub-core/commands/blsuki.c
> > +++ b/grub-core/commands/blsuki.c
> > @@ -1510,6 +1510,12 @@ blsuki_is_default_entry (const char *def_entry, grub_blsuki_entry_t *entry,
> > int
> >      return true;
> > 
> >    def_idx = grub_strtol (def_entry, &def_entry_end, 0);
> > +  if (grub_errno == GRUB_ERR_BAD_NUMBER)
> > +    {
> > +      grub_errno = GRUB_ERR_NONE;
> > +      return false;
> > +    }
> > +
> >    if (*def_entry_end != '\0' || def_idx < 0 || def_idx > GRUB_INT_MAX)
> >      return false;
> > 
> > --
> > 2.51.1
> > 
> > 
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