Re: [PATCH AUTOSEL 4.19 104/123] pstore/ram: Correctly calculate usable PRZ bytes

[Sasha Levin]

On Wed, Dec 05, 2018 at 02:57:08PM -0800, Kees Cook wrote:
> On Wed, Dec 5, 2018 at 1:41 AM Sasha Levin <sashal@xxxxxxxxxx> wrote:
> > From: Kees Cook <keescook@xxxxxxxxxxxx>
> >
> > [ Upstream commit 89d328f637b9904b6d4c9af73c8a608b8dd4d6f8 ]
> >
> > The actual number of bytes stored in a PRZ is smaller than the
> > bytes requested by platform data, since there is a header on each
> > PRZ. Additionally, if ECC is enabled, there are trailing bytes used
> > as well. Normally this mismatch doesn't matter since PRZs are circular
> > buffers and the leading "overflow" bytes are just thrown away. However, in
> > the case of a compressed record, this rather badly corrupts the results.
> >
> > This corruption was visible with "ramoops.mem_size=204800 ramoops.ecc=1".
> > Any stored crashes would not be uncompressable (producing a pstorefs
> > "dmesg-*.enc.z" file), and triggering errors at boot:
> >
> >   [    2.790759] pstore: crypto_comp_decompress failed, ret = -22!
> >
> > Backporting this depends on commit 70ad35db3321 ("pstore: Convert console
> > write to use ->write_buf")
>
> Please note the above. If this gets backported, this one is needed too.

Okay, I've added 70ad35db3321 for 4.9, 4.4, and 3.18.

--
Thanks,
Sasha