Re: [PATCH v2] platform/x86: hp-wmi: fix heap OOB read and memory corruption in hp_wmi_perform_query()

[Muhammad Bilal]

ping.

On Wed, Aug 26, 2026 at 3:30 PM Muhammad Bilal <meatuni001@xxxxxxxxx> wrote:
>
> hp_wmi_perform_query() evaluates an ACPI WMI method and expects a
> struct bios_return header in the returned buffer. However, it only
> checks that the ACPI object type is ACPI_TYPE_BUFFER without verifying
> that obj->buffer.length is at least sizeof(*bios_return) (8 bytes).
>
> If the firmware or ACPI method returns a buffer shorter than 8 bytes:
>
> 1. bios_return->return_code at offset 4 reads out of bounds from the
>    allocated ACPI buffer slab.
>
> 2. If return_code evaluates to 0 and outsize is non-zero,
>    (int)(obj->buffer.length - sizeof(*bios_return)) evaluates to a
>    negative integer (e.g. -8 for a 0-length buffer). actual_outsize is
>    set to this negative value and passed to memcpy(buffer, ...,
>    actual_outsize), where the signed negative value is cast to
>    size_t (e.g. 0xfffffffffffffff8), attempting to copy ~18 Exabytes
>    and triggering an immediate kernel crash. Additionally,
>    memset(buffer + actual_outsize, ...) performs an out-of-bounds
>    write before buffer.
>
> Fix this by ensuring obj->buffer.length is at least sizeof(*bios_return)
> before accessing the return code, and compute actual_outsize safely
> using min_t(u32, ...), which is sound specifically because the guard
> above already rules out obj->buffer.length being smaller than
> sizeof(*bios_return) by the time that subtraction runs.
>
> Fixes: c3021ea1beee ("hp-wmi: allow setting input and output buffer sizes separately")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Muhammad Bilal <meatuni001@xxxxxxxxx>
> ---
> v2: Rebased onto current platform-drivers-x86.git 'fixes' (confirmed
>     matching current mainline, blob b2773fc1aca414792b99406315496a2c3a64dd06).
>     v1 was diffed against a stale local copy of hp-wmi.c that predated
>     a batch of unrelated upstream changes (GPU MUX switch support, new
>     OMEN/Victus board IDs), so its hunks no longer applied. The fix
>     itself is unchanged, only the base and line numbers moved. Also
>     correcting the recipient list: Hans de Goede's address is
>     hdegoede@xxxxxxxxxx, not hansg@xxxxxxxxxx as v1 had it.
>
>  drivers/platform/x86/hp/hp-wmi.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/platform/x86/hp/hp-wmi.c b/drivers/platform/x86/hp/hp-wmi.c
> index b2773fc..d7ad206 100644
> --- a/drivers/platform/x86/hp/hp-wmi.c
> +++ b/drivers/platform/x86/hp/hp-wmi.c
> @@ -691,8 +691,9 @@ static int hp_wmi_perform_query(int query, enum hp_wmi_command command,
>                 goto out_free;
>         }
>
> -       if (obj->type != ACPI_TYPE_BUFFER) {
> -               pr_warn("query 0x%x returned an invalid object 0x%x\n", query, ret);
> +       if (obj->type != ACPI_TYPE_BUFFER ||
> +           obj->buffer.length < sizeof(*bios_return)) {
> +               pr_warn("query 0x%x returned wrong type or too small buffer\n", query);
>                 ret = -EINVAL;
>                 goto out_free;
>         }
> @@ -711,7 +712,7 @@ static int hp_wmi_perform_query(int query, enum hp_wmi_command command,
>         if (!outsize)
>                 goto out_free;
>
> -       actual_outsize = min(outsize, (int)(obj->buffer.length - sizeof(*bios_return)));
> +       actual_outsize = min_t(u32, outsize, obj->buffer.length - sizeof(*bios_return));
>         memcpy(buffer, obj->buffer.pointer + sizeof(*bios_return), actual_outsize);
>         memset(buffer + actual_outsize, 0, outsize - actual_outsize);
>
> --
> 2.55.0
>