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Date: Fri, 15 Dec 2017 08:22:32 +0100
Message-ID: <s5hmv2kwj47.wl-tiwai@suse.de>
From: Takashi Iwai <tiwai@suse.de>
To: "Rafael J. Wysocki" <rafael@kernel.org>
Cc: Kees Cook <keescook@chromium.org>, Anton Vorontsov <anton@enomsg.org>,
        Colin Cross <ccross@android.com>, Tony Luck <tony.luck@intel.com>,
        "Rafael J . Wysocki" <rjw@rjwysocki.net>, Jerry Tang <jtang@suse.com>,
        Borislav Petkov <bp@alien8.de>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] APEI / ERST: Fix missing error handling in erst_reader()
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        <CAJZ5v0gAiSiwwcWpHXWGEpo_Tjy4tqy1D5XvL==BJeuQ6LRKOg@mail.gmail.com>
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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@suse.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@vger.kernel.org>
> > Tested-by: Jerry Tang <jtang@suse.com>
> > Signed-off-by: Takashi Iwai <tiwai@suse.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.


Takashi