linux-kernel - Re: arm64: libgpiod: refcount_t: underflow; use-after-free.

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Date:   Wed, 7 Jun 2023 20:35:34 +0200
From:   Anders Roxell <anders.roxell@...aro.org>
To:     Bartosz Golaszewski <brgl@...ev.pl>
Cc:     Naresh Kamboju <naresh.kamboju@...aro.org>,
        Linux Media Mailing List <linux-media@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>,
        "open list:GPIO SUBSYSTEM" <linux-gpio@...r.kernel.org>,
        lkft-triage@...ts.linaro.org,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Ferry Toth <fntoth@...il.com>,
        Linus Walleij <linus.walleij@...aro.org>, warthog618@...il.com,
        Arnd Bergmann <arnd@...db.de>
Subject: Re: arm64: libgpiod: refcount_t: underflow; use-after-free.

On Wed, 22 Feb 2023 at 13:36, Bartosz Golaszewski <brgl@...ev.pl> wrote:
>
> On Mon, Feb 20, 2023 at 3:59 PM Naresh Kamboju
> <naresh.kamboju@...aro.org> wrote:
> >
> > Following kernel warning notices on qemu-arm64, qemu-arm and also on devices
> > running Linux version v6.2.0 while running libgpiod tests.
> >
>
> I don't see it on v6.2 with libgpiod v1.6.4. Seeing the output of the
> test script, it seems you're using an old version - what is it?

Yes, I did run libgpiod v1.6.4 by mistake on todays next-20230607 tag.
Not sure if I should or should not get the use-after-free warning by
running the "wrong version"
of a test suite or?

>
> > + ./gpiod.sh /opt/libgpiod/bin/
>
> What's in gpiod.sh?

its a wrapper script around gpiod-test [1] to parse the output to be
understood by our test framework

Cheers,
Anders
[1] https://github.com/Linaro/test-definitions/blob/master/automated/linux/gpiod/gpiod.sh

>
> Bart
>
> >   [INFO]    libgpiod test suite
> >   [INFO]    117 tests registered
> >   [INFO]    checking the linux kernel version
> >   [INFO]    kernel release is v6.2.0 - ok to run tests
> >   [INFO]    using gpio-tools from '/usr/bin'
> > [   10.499036] ------------[ cut here ]------------
> > [   10.499656] refcount_t: underflow; use-after-free.
> > [   10.500264] WARNING: CPU: 2 PID: 291 at lib/refcount.c:28
> > refcount_warn_saturate+0xf4/0x144
> > [   10.501306] Modules linked in: gpio_mockup(-) cfg80211 bluetooth
> > rfkill crct10dif_ce fuse drm
> > [   10.502364] CPU: 2 PID: 291 Comm: gpiod-test Not tainted 6.2.0 #1
> > [   10.503229] Hardware name: linux,dummy-virt (DT)
> > [   10.503883] pstate: 60400005 (nZCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> > [   10.505331] pc : refcount_warn_saturate+0xf4/0x144
> > [   10.505723] lr : refcount_warn_saturate+0xf4/0x144
> > [   10.506115] sp : ffff800008983cd0
> > [   10.506391] x29: ffff800008983cd0 x28: ffff0000c4c4c100 x27: 0000000000000000
> > [   10.506961] x26: 0000000000000000 x25: 0000000000000000 x24: 0000000000000000
> > [   10.507533] x23: 0000000000000200 x22: ffff0000c4e66800 x21: ffff0000c7734640
> > [   10.508104] x20: 0000000000000001 x19: ffff0000c7734600 x18: ffffffffffffffff
> > [   10.508677] x17: 3d4d455453595342 x16: ffffcf0234432020 x15: ffff800088983957
> > [   10.509424] x14: 0000000000000000 x13: 2e656572662d7265 x12: 7466612d65737520
> > [   10.510003] x11: 3b776f6c66726564 x10: ffffcf02365db580 x9 : ffffcf0233b20138
> > [   10.510575] x8 : 00000000ffffefff x7 : ffffcf02365db580 x6 : 0000000000000001
> > [   10.511145] x5 : ffffcf023655f000 x4 : ffffcf023655f2e8 x3 : 0000000000000000
> > [   10.511721] x2 : 0000000000000000 x1 : 0000000000000000 x0 : ffff0000c4c4c100
> > [   10.512294] Call trace:
> > [   10.512494]  refcount_warn_saturate+0xf4/0x144
> > [   10.512971]  kobject_put+0x164/0x220
> > [   10.513224]  fwnode_remove_software_node+0x44/0x60
> > [   10.513554]  gpio_mockup_unregister_pdevs+0x54/0x70 [gpio_mockup]
> > [   10.513970]  gpio_mockup_exit+0x10/0x328 [gpio_mockup]
> > [   10.514322]  __arm64_sys_delete_module+0x190/0x2a0
> > [   10.514653]  invoke_syscall+0x50/0x120
> > [   10.514915]  el0_svc_common.constprop.0+0x104/0x124
> > [   10.515277]  do_el0_svc+0x44/0xcc
> > [   10.515541]  el0_svc+0x30/0x94
> > [   10.515788]  el0t_64_sync_handler+0xbc/0x13c
> > [   10.516126]  el0t_64_sync+0x190/0x194
> > [   10.516419] ---[ end trace 0000000000000000 ]---
> >
> >
> > Build and test logs,
> > https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2/testrun/14856342/suite/libgpiod/test/ctxless-get-value-single-line/log
> > https://qa-reports.linaro.org/lkft/linux-mainline-master/build/v6.2/testrun/14856342/suite/libgpiod/tests/
> >
> >
> > --
> > Linaro LKFT
> > https://lkft.linaro.org