ACPICA: Linuxize: Fix a NULL pointer dereference in acpi_db_convert_to_package()

In acpi_db_convert_to_package(), the variable elements is assigned by
ACPI_ALLOCATE_ZEROED() and passes its address to 
acpi_db_convert_to_object(). In that function we may have a dereference
of elements without checks. ACPI_ALLOCATE_ZEROED() would return NULL on
failure, which may lead to NULL pointer dereference.

Fix this bug by adding a NULL check of elements.

This bug was found by a static analyzer.

Builds with 'make allyesconfig' show no new warnings,
and our static analyzer no longer warns about this code.

Fixes: 995751025572 ("ACPICA: Linuxize: Export debugger files to Linux")
Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
---
The analysis employs differential checking to identify inconsistent 
security operations (e.g., checks or kfrees) between two code paths 
and confirms that the inconsistent operations are not recovered in the
current function or the callers, so they constitute bugs. 

Note that, as a bug found by static analysis, it can be a false
positive or hard to trigger. Multiple researchers have cross-reviewed
the bug.

 drivers/acpi/acpica/dbconvert.c | 2 ++
 1 file changed, 2 insertions(+)

On Mon, Jan 24, 2022 at 5:45 PM Zhou Qingyang <zhou1615@umn.edu> wrote:
>
> In acpi_db_convert_to_package(), the variable elements is assigned by
> ACPI_ALLOCATE_ZEROED() and passes its address to
> acpi_db_convert_to_object(). In that function we may have a dereference
> of elements without checks. ACPI_ALLOCATE_ZEROED() would return NULL on
> failure, which may lead to NULL pointer dereference.
>
> Fix this bug by adding a NULL check of elements.
>
> This bug was found by a static analyzer.
>
> Builds with 'make allyesconfig' show no new warnings,
> and our static analyzer no longer warns about this code.
>
> Fixes: 995751025572 ("ACPICA: Linuxize: Export debugger files to Linux")
> Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>

This is ACPICA material and so it should be submitted as a change
against the upstream code via https://github.com/acpica/acpica

Thanks!

> ---
> The analysis employs differential checking to identify inconsistent
> security operations (e.g., checks or kfrees) between two code paths
> and confirms that the inconsistent operations are not recovered in the
> current function or the callers, so they constitute bugs.
>
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
>
>  drivers/acpi/acpica/dbconvert.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/acpi/acpica/dbconvert.c b/drivers/acpi/acpica/dbconvert.c
> index 2b84ac093698..8dbab6932049 100644
> --- a/drivers/acpi/acpica/dbconvert.c
> +++ b/drivers/acpi/acpica/dbconvert.c
> @@ -174,6 +174,8 @@ acpi_status acpi_db_convert_to_package(char *string, union acpi_object *object)
>         elements =
>             ACPI_ALLOCATE_ZEROED(DB_DEFAULT_PKG_ELEMENTS *
>                                  sizeof(union acpi_object));
> +       if (!elements)
> +               return (AE_NO_MEMORY);
>
>         this = string;
>         for (i = 0; i < (DB_DEFAULT_PKG_ELEMENTS - 1); i++) {
> --
> 2.25.1
>

On Tue, Jan 25, 2022 at 12:40:14AM +0800, Zhou Qingyang wrote:
> In acpi_db_convert_to_package(), the variable elements is assigned by
> ACPI_ALLOCATE_ZEROED() and passes its address to 
> acpi_db_convert_to_object(). In that function we may have a dereference
> of elements without checks. ACPI_ALLOCATE_ZEROED() would return NULL on
> failure, which may lead to NULL pointer dereference.
> 
> Fix this bug by adding a NULL check of elements.
> 
> This bug was found by a static analyzer.
> 
> Builds with 'make allyesconfig' show no new warnings,
> and our static analyzer no longer warns about this code.
> 
> Fixes: 995751025572 ("ACPICA: Linuxize: Export debugger files to Linux")
> Signed-off-by: Zhou Qingyang <zhou1615@umn.edu>
> ---
> The analysis employs differential checking to identify inconsistent 
> security operations (e.g., checks or kfrees) between two code paths 
> and confirms that the inconsistent operations are not recovered in the
> current function or the callers, so they constitute bugs. 
> 
> Note that, as a bug found by static analysis, it can be a false
> positive or hard to trigger. Multiple researchers have cross-reviewed
> the bug.
> 
>  drivers/acpi/acpica/dbconvert.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/acpi/acpica/dbconvert.c b/drivers/acpi/acpica/dbconvert.c
> index 2b84ac093698..8dbab6932049 100644
> --- a/drivers/acpi/acpica/dbconvert.c
> +++ b/drivers/acpi/acpica/dbconvert.c
> @@ -174,6 +174,8 @@ acpi_status acpi_db_convert_to_package(char *string, union acpi_object *object)
>  	elements =
>  	    ACPI_ALLOCATE_ZEROED(DB_DEFAULT_PKG_ELEMENTS *
>  				 sizeof(union acpi_object));
> +	if (!elements)
> +		return (AE_NO_MEMORY);
>  
>  	this = string;
>  	for (i = 0; i < (DB_DEFAULT_PKG_ELEMENTS - 1); i++) {
> -- 
> 2.25.1
>

As stated before, umn.edu is still not allowed to contribute to the
Linux kernel.  Please work with your administration to resolve this
issue.