On my Dell Inspiron 3505, the battery model name was displayed
differently than when running Windows. While i first suspected an
ACPI issue, it turned out that the real reason was the ACPI battery
driver failing to handle strings larger than 32 bytes.

This caused the model name of the battery (35 bytes long, hex string)
to miss proper NUL-termination, resulting in a buffer overread later.
Luckily, a valid string was stored right after the now invalid string,
appending only the battery serial number to the original model name.

The first patch fixes a potential buffer overread then handling buffers,
while the second patch finally increases the maximum string length to
avoid truncating such larger strings.

The patch series was tested on a Dell Inspiron 3505 and appears
to work properly.
---
Changes in v2:
- Drop first patch since it was already applied
- combine the second and third patch
- do not replace 0 with '\0'
- spell ACPI in capitals
- rework the buffer length hdanling

Armin Wolf (2):
  ACPI: battery: Fix buffer overread if not NUL-terminated
  ACPI: battery: Increase maximum string length

 drivers/acpi/battery.c | 35 +++++++++++++++++++++++------------
 1 file changed, 23 insertions(+), 12 deletions(-)

--
2.30.2

Am 19.01.23 um 15:21 schrieb Armin Wolf:

> On my Dell Inspiron 3505, the battery model name was displayed
> differently than when running Windows. While i first suspected an
> ACPI issue, it turned out that the real reason was the ACPI battery
> driver failing to handle strings larger than 32 bytes.
>
> This caused the model name of the battery (35 bytes long, hex string)
> to miss proper NUL-termination, resulting in a buffer overread later.
> Luckily, a valid string was stored right after the now invalid string,
> appending only the battery serial number to the original model name.
>
> The first patch fixes a potential buffer overread then handling buffers,
> while the second patch finally increases the maximum string length to
> avoid truncating such larger strings.
>
> The patch series was tested on a Dell Inspiron 3505 and appears
> to work properly.

Are there any outstanding issues with the patch series which need
to be fixed for mainline inclusion?

Armin Wolf

> ---
> Changes in v2:
> - Drop first patch since it was already applied
> - combine the second and third patch
> - do not replace 0 with '\0'
> - spell ACPI in capitals
> - rework the buffer length hdanling
>
> Armin Wolf (2):
>    ACPI: battery: Fix buffer overread if not NUL-terminated
>    ACPI: battery: Increase maximum string length
>
>   drivers/acpi/battery.c | 35 +++++++++++++++++++++++------------
>   1 file changed, 23 insertions(+), 12 deletions(-)
>
> --
> 2.30.2
>
>

On Mon, Jan 30, 2023 at 10:14 AM Armin Wolf <W_Armin@gmx.de> wrote:
>
> Am 19.01.23 um 15:21 schrieb Armin Wolf:
>
> > On my Dell Inspiron 3505, the battery model name was displayed
> > differently than when running Windows. While i first suspected an
> > ACPI issue, it turned out that the real reason was the ACPI battery
> > driver failing to handle strings larger than 32 bytes.
> >
> > This caused the model name of the battery (35 bytes long, hex string)
> > to miss proper NUL-termination, resulting in a buffer overread later.
> > Luckily, a valid string was stored right after the now invalid string,
> > appending only the battery serial number to the original model name.
> >
> > The first patch fixes a potential buffer overread then handling buffers,
> > while the second patch finally increases the maximum string length to
> > avoid truncating such larger strings.
> >
> > The patch series was tested on a Dell Inspiron 3505 and appears
> > to work properly.
>
> Are there any outstanding issues with the patch series which need
> to be fixed for mainline inclusion?

I'll have a look shortly and let you know.

Thanks!

> > ---
> > Changes in v2:
> > - Drop first patch since it was already applied
> > - combine the second and third patch
> > - do not replace 0 with '\0'
> > - spell ACPI in capitals
> > - rework the buffer length hdanling
> >
> > Armin Wolf (2):
> >    ACPI: battery: Fix buffer overread if not NUL-terminated
> >    ACPI: battery: Increase maximum string length
> >
> >   drivers/acpi/battery.c | 35 +++++++++++++++++++++++------------
> >   1 file changed, 23 insertions(+), 12 deletions(-)
> >
> > --

On Mon, Jan 30, 2023 at 1:29 PM Rafael J. Wysocki <rafael@kernel.org> wrote:
>
> On Mon, Jan 30, 2023 at 10:14 AM Armin Wolf <W_Armin@gmx.de> wrote:
> >
> > Am 19.01.23 um 15:21 schrieb Armin Wolf:
> >
> > > On my Dell Inspiron 3505, the battery model name was displayed
> > > differently than when running Windows. While i first suspected an
> > > ACPI issue, it turned out that the real reason was the ACPI battery
> > > driver failing to handle strings larger than 32 bytes.
> > >
> > > This caused the model name of the battery (35 bytes long, hex string)
> > > to miss proper NUL-termination, resulting in a buffer overread later.
> > > Luckily, a valid string was stored right after the now invalid string,
> > > appending only the battery serial number to the original model name.
> > >
> > > The first patch fixes a potential buffer overread then handling buffers,
> > > while the second patch finally increases the maximum string length to
> > > avoid truncating such larger strings.
> > >
> > > The patch series was tested on a Dell Inspiron 3505 and appears
> > > to work properly.
> >
> > Are there any outstanding issues with the patch series which need
> > to be fixed for mainline inclusion?
>
> I'll have a look shortly and let you know.

I've queued up the patches for 6.3, thanks!