linux-kernel - Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft

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Date:   Wed, 27 Jan 2021 19:48:08 +0100
From:   Dmitry Vyukov <dvyukov@...gle.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:     George Kennedy <george.kennedy@...cle.com>,
        kasan-dev <kasan-dev@...glegroups.com>,
        Alexander Potapenko <glider@...gle.com>,
        Andrey Ryabinin <aryabinin@...tuozzo.com>, pjones@...hat.com,
        konrad@...nel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/1] iscsi_ibft: KASAN false positive failure occurs in ibft_init()

On Wed, Jan 27, 2021 at 7:44 PM Konrad Rzeszutek Wilk
<konrad.wilk@...cle.com> wrote:
>
> On Tue, Jan 26, 2021 at 01:03:21PM -0500, George Kennedy wrote:
> > During boot of kernel with CONFIG_KASAN the following KASAN false
> > positive failure will occur when ibft_init() reads the
> > ACPI iBFT table: BUG: KASAN: use-after-free in ibft_init
> >
> > The ACPI iBFT table is not allocated, and the iscsi driver uses
> > a pointer to it to calculate checksum, etc. KASAN complains
> > about this pointer with use-after-free, which this is not.
> >
>
> Andrey, Alexander, Dmitry,
>
> I think this is the right way for this, but was wondering if you have
> other suggestions?
>
> Thanks!

Hi George, Konrad,

Please provide a sample KASAN report and kernel version to match line numbers.

Why does KASAN think the address is freed? For that to happen that
memory should have been freed. I don't remember any similar false
positives from KASAN, so this looks a bit suspicious.


> > Signed-off-by: George Kennedy <george.kennedy@...cle.com>
> > ---
> >  drivers/firmware/Makefile | 3 +++
> >  1 file changed, 3 insertions(+)
> >
> > diff --git a/drivers/firmware/Makefile b/drivers/firmware/Makefile
> > index 5e013b6..30ddab5 100644
> > --- a/drivers/firmware/Makefile
> > +++ b/drivers/firmware/Makefile
> > @@ -14,6 +14,9 @@ obj-$(CONFIG_INTEL_STRATIX10_SERVICE) += stratix10-svc.o
> >  obj-$(CONFIG_INTEL_STRATIX10_RSU)     += stratix10-rsu.o
> >  obj-$(CONFIG_ISCSI_IBFT_FIND)        += iscsi_ibft_find.o
> >  obj-$(CONFIG_ISCSI_IBFT)     += iscsi_ibft.o
> > +KASAN_SANITIZE_iscsi_ibft.o := n
> > +KCOV_INSTRUMENT_iscsi_ibft.o := n
> > +
> >  obj-$(CONFIG_FIRMWARE_MEMMAP)        += memmap.o
> >  obj-$(CONFIG_RASPBERRYPI_FIRMWARE) += raspberrypi.o
> >  obj-$(CONFIG_FW_CFG_SYSFS)   += qemu_fw_cfg.o
> > --
> > 1.8.3.1
> >