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

Am 10.11.2025 um 08:38 schrieb Michael Chang via Grub-devel:
> 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.
> 
> 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;
>  
This way you'll clear a possible previous GRUB_ERR_BAD_NUMBER
Shouldn't it be this way:
     return true;

+  old_err = grub_errno;
+  grub_errno = GRUB_ERR_NONE;
   def_idx = grub_strtol (def_entry, &def_entry_end, 0);
+  if (grub_errno == GRUB_ERR_BAD_NUMBER)
+    {
+      grub_errno = old_err;
+      return false;
+    }
+    grub_errno = old_err;
+
   if (*def_entry_end != '\0' || def_idx < 0 || def_idx > GRUB_INT_MAX)
     return false;

JMTC
KR Michael

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