linux-kernel - Re: [PATCH] APEI / ERST: Fix missing error handling in erst

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Message-ID: <20171215105242.ed7b2nsanwgmoxl6@pd.tnic>
Date:   Fri, 15 Dec 2017 11:52:42 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Takashi Iwai <tiwai@...e.de>
Cc:     "Rafael J. Wysocki" <rafael@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Anton Vorontsov <anton@...msg.org>,
        Colin Cross <ccross@...roid.com>,
        Tony Luck <tony.luck@...el.com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Jerry Tang <jtang@...e.com>,
        ACPI Devel Maling List <linux-acpi@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] APEI / ERST: Fix missing error handling in erst_reader()

On Fri, Dec 15, 2017 at 08:22:32AM +0100, Takashi Iwai wrote:
> On Fri, 15 Dec 2017 02:01:20 +0100,
> Rafael J. Wysocki wrote:
> > 
> > On Thu, Dec 14, 2017 at 1:31 PM, Takashi Iwai <tiwai@...e.de> wrote:
> > > The commit f6f828513290 ("pstore: pass allocated memory region back to
> > > caller") changed the check of the return value from erst_read() in
> > > erst_reader() in the following way:
> > >
> > >         if (len == -ENOENT)
> > >                 goto skip;
> > > -       else if (len < 0) {
> > > -               rc = -1;
> > > +       else if (len < sizeof(*rcd)) {
> > > +               rc = -EIO;
> > >                 goto out;
> > >
> > > This introduced another bug: since the comparison with sizeof() is
> > > cast to unsigned, a negative len value doesn't hit any longer.
> > > As a result, when an error is returned from erst_read(), the code
> > > falls through, and it may eventually lead to some weird thing like
> > > memory corruption.
> > >
> > > This patch adds the negative error value check more explicitly for
> > > addressing the issue.
> > >
> > > Fixes: f6f828513290 ("pstore: pass allocated memory region back to caller")
> > 
> > That's ancient. :-)
> > 
> > > Cc: <stable@...r.kernel.org>
> > > Tested-by: Jerry Tang <jtang@...e.com>
> > > Signed-off-by: Takashi Iwai <tiwai@...e.de>
> > > ---
> > >  drivers/acpi/apei/erst.c | 2 +-
> > >  1 file changed, 1 insertion(+), 1 deletion(-)
> > >
> > > diff --git a/drivers/acpi/apei/erst.c b/drivers/acpi/apei/erst.c
> > > index 6742f6c68034..9bff853e85f3 100644
> > > --- a/drivers/acpi/apei/erst.c
> > > +++ b/drivers/acpi/apei/erst.c
> > > @@ -1007,7 +1007,7 @@ static ssize_t erst_reader(struct pstore_record *record)
> > >         /* The record may be cleared by others, try read next record */
> > >         if (len == -ENOENT)
> > >                 goto skip;
> > > -       else if (len < sizeof(*rcd)) {
> > > +       else if (len < 0 || len < sizeof(*rcd)) {
> > >                 rc = -EIO;
> > >                 goto out;
> > >         }
> > > --
> > 
> > OK, I'm going to queue this up unless I see objections from Boris or Tony.
> 
> I missed Boris in Cc list, sorry.  Now added.

LGTM.

Reviewed-by: Borislav Petkov <bp@...e.de>

-- 
Regards/Gruss,
    Boris.

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