[PATCH u-boot] regmap: fix a serious pointer casting bug

[Bin Meng]

Hi Simon,

On Tue, Mar 16, 2021 at 2:10 PM Simon Glass <sjg at chromium.org> wrote:
>
> Hello Marek,
>
> On 03.03.21 14:15, Marek Behún wrote:
> > There is a serious bug in regmap_read() and regmap_write() functions
> > where an uint pointer is cast to (void *) which is then cast to (u8 *),
> > (u16 *), (u32 *) or (u64 *), depending on register width of the map.
> >
> > For example given a regmap with 16-bit register width the code
> >       int val = 0x12340000;
> >       regmap_read(map, 0, &val);
> > only changes the lower 16 bits of val on little-endian machines.
> > The upper 16 bits will remain 0x1234.
> >
> > Nobody noticed this probably because this bug can be triggered with
> > regmap_write() only on big-endian architectures (which are not used by
> > many people anymore), and on little endian this bug has consequences
> > only if register width is 8 or 16 bits and also the memory place to
> > which regmap_read() should store it's result has non-zero upper bits,
> > which it seems doesn't happen anywhere in U-Boot normally. CI managed to
> > trigger this bug in unit test of dm_test_devm_regmap_field when compiled
> > for sandbox_defconfig using LTO.
> >
> > Fix this simply by taking into account that regmap_raw_read() and
> > regmap_raw_write() behave as if the data given to these functions were
> > in little-endian format, i.e. use cpu_to_le32() / le32_to_cpu(). In
> > regmap_read() also zero out the space so that we don't get invalid
> > result if regmap_raw_read() does not fill the whole object.
> >
> > Signed-off-by: Marek Behún <marek.behun at nic.cz>
> > ---
> >  drivers/core/regmap.c | 13 ++++++++++++-
> >  1 file changed, 12 insertions(+), 1 deletion(-)
>
> Good catch, thanks!
>
> Reviewed-by: Heiko Schocher <hs at denx.de>
>
> bye,
> Heiko
> --
> DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
> HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
> Phone: +49-8142-66989-52   Fax: +49-8142-66989-80   Email: hs at denx.de
>
> Applied to u-boot-dm/next, thanks!

This patch is included in the LTO series.

Regards,
Bin