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

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

[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 <mchang@suse.com>
---
 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


_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

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

[Sudhakar Kuppusamy]

> On 10 Nov 2025, at 1:08 PM, Michael Chang via Grub-devel <grub-devel@gnu.org> 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.
> 
> Signed-off-by: Michael Chang <mchang@suse.com>

Reviewed-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>


Thanks,
Sudhakar  
> ---
> 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
> 
> 
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> https://lists.gnu.org/mailman/listinfo/grub-devel


_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

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

[Michael Lawnick via Grub-devel]

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 <mchang@suse.com>
> ---
>  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

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

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

[Avnish Chouhan]

On 2025-11-10 19:06, grub-devel-request@gnu.org wrote:
> Message: 3
> Date: Mon, 10 Nov 2025 15:38:13 +0800
> From: Michael Chang <mchang@suse.com>
> To: The development of GNU GRUB <grub-devel@gnu.org>
> Subject: [PATCH] blsuki: Fix grub_errno leakage in
> 	blsuki_is_default_entry()
> Message-ID: <20251110073813.20146-1-mchang@suse.com>
> 
> 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 <mchang@suse.com>

Reviewed-by: Avnish Chouhan <avnish@linux.ibm.com>

Regards,
Avnish Chouhan

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

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

[Alec Brown via Grub-devel]

On Mon, Nov 10, 2025 at 2:38 AM, Michael Chang <mchang@suse.com> 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.

Alec Brown

> 
> Signed-off-by: Michael Chang <mchang@suse.com>
> ---
>  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
> 
> 
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> https://urldefense.com/v3/__https://lists.gnu.org/mailman/listinfo/grub-
> devel__;!!ACWV5N9M2RV99hQ!PT07VdaZpBxwaIforN0iXRL1OG2vC6xOV2SQ6cgn5eVQvHxGFpEtx3c9eNW_ApT4iml6Fnoj
> FNjVxarvCu1C$
_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

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

[Michael Chang via Grub-devel]

On Mon, Nov 10, 2025 at 03:55:03PM +0100, Michael Lawnick via Grub-devel wrote:
> 
> 
> 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 <mchang@suse.com>
> > ---
> >  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:

No, I think this patch does not introduce such behavior change. The
previous error of any kind is not considered an issue, and there was no
intent to preserve them unless grub_strtol() was explicitly surrounded
by grub_error_push()/grub_error_pop(), but apparantly it is not there
before the patch is applied. The error return is always overridden by
the error return code of grub_strtol() if there's any.

>      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;
> +

IMHO restoring unhandled grub_errno here would still be considered a
bug. It could spread to other unrelated modules or functions which might
interpret it as an unspecified/unknown error and thus disrupt the boot
process in one way or another. This is exactly what the patch trying to
avoid.

Thanks,
Michael


>    if (*def_entry_end != '\0' || def_idx < 0 || def_idx > GRUB_INT_MAX)
>      return false;
> 
> JMTC
> KR Michael
> 
> _______________________________________________
> Grub-devel mailing list
> Grub-devel@gnu.org
> https://lists.gnu.org/mailman/listinfo/grub-devel

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

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

[Michael Chang via Grub-devel]

Hi,

Sorry. Forgot to mention the downstream bug report which was fixed by
the patch.

https://bugzilla.suse.com/show_bug.cgi?id=1253097

Thanks,
Michael

On Mon, Nov 10, 2025 at 03:38:13PM +0800, Michael Chang 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.
> 
> Signed-off-by: Michael Chang <mchang@suse.com>
> ---
>  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
> 

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

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

[Michael Chang via Grub-devel]

On Mon, Nov 10, 2025 at 05:26:02PM +0000, Alec Brown wrote:
> On Mon, Nov 10, 2025 at 2:38 AM, Michael Chang <mchang@suse.com> 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 <mchang@suse.com>
> > ---
> >  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
> > 
> > 
> > _______________________________________________
> > Grub-devel mailing list
> > Grub-devel@gnu.org
> > https://urldefense.com/v3/__https://lists.gnu.org/mailman/listinfo/grub-
> > devel__;!!ACWV5N9M2RV99hQ!PT07VdaZpBxwaIforN0iXRL1OG2vC6xOV2SQ6cgn5eVQvHxGFpEtx3c9eNW_ApT4iml6Fnoj
> > FNjVxarvCu1C$

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

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

[Michael Chang via Grub-devel]

On Mon, Nov 10, 2025 at 08:34:18PM +0530, Avnish Chouhan wrote:
> On 2025-11-10 19:06, grub-devel-request@gnu.org wrote:
> > Message: 3
> > Date: Mon, 10 Nov 2025 15:38:13 +0800
> > From: Michael Chang <mchang@suse.com>
> > To: The development of GNU GRUB <grub-devel@gnu.org>
> > Subject: [PATCH] blsuki: Fix grub_errno leakage in
> > 	blsuki_is_default_entry()
> > Message-ID: <20251110073813.20146-1-mchang@suse.com>
> > 
> > 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 <mchang@suse.com>
> 
> Reviewed-by: Avnish Chouhan <avnish@linux.ibm.com>

Thanks a lot for the review. I'll add your Reviewed-by tag in next
version.

Thanks,
Michael

> 
> Regards,
> Avnish Chouhan

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel

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

[Michael Chang via Grub-devel]

On Mon, Nov 10, 2025 at 07:05:10PM +0530, Sudhakar Kuppusamy wrote:
> 
> 
> > On 10 Nov 2025, at 1:08 PM, Michael Chang via Grub-devel <grub-devel@gnu.org> 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.
> > 
> > Signed-off-by: Michael Chang <mchang@suse.com>
> 
> Reviewed-by: Sudhakar Kuppusamy <sudhakar@linux.ibm.com>

Thanks for the review. I'll add your Reviewed-by tag in next version.

Thanks,
Michael

> 
> 
> Thanks,
> Sudhakar  
> > ---
> > 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
> > 
> > 
> > _______________________________________________
> > Grub-devel mailing list
> > Grub-devel@gnu.org
> > https://lists.gnu.org/mailman/listinfo/grub-devel
> 

_______________________________________________
Grub-devel mailing list
Grub-devel@gnu.org
https://lists.gnu.org/mailman/listinfo/grub-devel