Hi Prabhakar,
On Mon, Sep 7, 2020 at 11:27 PM Lad, Prabhakar
<prabhakar.csengg@xxxxxxxxx> wrote:
> On Mon, Sep 7, 2020 at 1:05 PM Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote:
> > On Fri, Sep 4, 2020 at 11:04 AM Lad, Prabhakar
> > <prabhakar.csengg@xxxxxxxxx> wrote:
> > > I am seeing "Unable to handle kernel paging request at virtual address
> > > xxxxxxxxxx" panic while running bonnie++ (version 1.04). I have
> > > managed to replicate this issue on R-Car M3N, G2[HMN]. I have been
> > > using renesas_defconfig for all the platforms and I have tested on
> > > Linux 5.9.0-rc3 for all the 4 platforms.
> > >
> > > Initially I was testing bonnie++ on eMMC device and later discovered
> > > even running bonnie++ on NFS mount is causing this issue. I have
> > > attached the logs for M3N while running bonnie++ on NFS and logs for
> > > G2N while running on eMMC.
> > >
> > > I even traced back to 5.2 kernel where initial G2M support was added
> > > and still able to see this issue.
> >
> > Thanks for your report!
> >
> > While the crash symptoms seem to be the same in all crash logs, the
> > backtraces aren't.
> >
> > Does disabling SMP (maxcpus=1) help?
> unfortunately no.
OK, so it's not an SMP issue.
> > Does switching from SLUB to SLAB, and enabling CONFIG_DEBUG_SLAB
> > reveal memory corruption?
> >
> attached are the logs for SLUB and SLAB with debug enabled on G2M
> rev.4.0 board (bonnie++-1.04) all the 4 combinations cause the kernel
> panic!
>
> SLUB -> 1 CPU -> BUG radix_tree_node (Not tainted): Padding overwritten.
> SLUB -> all 6 CPU's -> BUG kmalloc-2k (Not tainted): Padding overwritten.
>
> SLAB -> 1 CPU -> Slab corruption (Not tainted): nfs_write_data
> start=ffff000016c08840, len=912
> SLAB -> all 6 CPU's -> Unable to handle kernel paging request at
> virtual address 7d81858c9c9d9dd0 ([7d81858c9c9d9dd0] address between
> user and kernel address ranges)
OK. So now we know something's overwriting its memory block. Either
it's writing too far, or a use-after-free case.
Now comes the hard part of finding who's responsible...
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
