Re: [uml-user] WARNING: at mm/slab_common.c:376 kmalloc_slab+0x33/0x80()

[richard -rw- weinberger <richard.weinberger@gmail.com>]

On Fri, May 10, 2013 at 11:52 PM, Toralf Förster <toralf.foerster@gmx.de> wrote:
> The bisected commit introduced this WARNING: on a user mode linux guest
> if the UML guest is fuzz tested with trinity :
>
>
> 2013-05-10T22:38:42.191+02:00 trinity kernel: ------------[ cut here ]------------
> 2013-05-10T22:38:42.191+02:00 trinity kernel: WARNING: at mm/slab_common.c:376 kmalloc_slab+0x33/0x80()
> 2013-05-10T22:38:42.191+02:00 trinity kernel: 40e2fda8:  [<08336928>] dump_stack+0x22/0x24
> 2013-05-10T22:38:42.191+02:00 trinity kernel: 40e2fdc0:  [<0807c2da>] warn_slowpath_common+0x5a/0x80
> 2013-05-10T22:38:42.191+02:00 trinity kernel: 40e2fde8:  [<0807c3a3>] warn_slowpath_null+0x23/0x30
> 2013-05-10T22:38:42.191+02:00 trinity kernel: 40e2fdf8:  [<080dfc93>] kmalloc_slab+0x33/0x80
> 2013-05-10T22:38:42.191+02:00 trinity kernel: 40e2fe0c:  [<080f8beb>] __kmalloc_track_caller+0x1b/0x110
> 2013-05-10T22:38:42.191+02:00 trinity kernel: 40e2fe30:  [<080dc866>] memdup_user+0x26/0x70
> 2013-05-10T22:38:42.191+02:00 trinity kernel: 40e2fe4c:  [<080dca6e>] strndup_user+0x3e/0x60
> 2013-05-10T22:38:42.191+02:00 trinity kernel: 40e2fe68:  [<0811ba60>] copy_mount_string+0x30/0x50
> 2013-05-10T22:38:42.195+02:00 trinity kernel: 40e2fe7c:  [<0811c46a>] sys_mount+0x1a/0xe0
> 2013-05-10T22:38:42.195+02:00 trinity kernel: 40e2feac:  [<08062b32>] handle_syscall+0x82/0xb0
> 2013-05-10T22:38:42.195+02:00 trinity kernel: 40e2fef4:  [<0807520d>] userspace+0x46d/0x590
> 2013-05-10T22:38:42.195+02:00 trinity kernel: 40e2ffec:  [<0805f7fc>] fork_handler+0x6c/0x70
> 2013-05-10T22:38:42.195+02:00 trinity kernel: 40e2fffc:  [<00000000>] 0x0
> 2013-05-10T22:38:42.195+02:00 trinity kernel:
> 2013-05-10T22:38:42.195+02:00 trinity kernel: ---[ end trace 17e5931469d0697d ]---
>
>
> Tested with host kernel 3.9.1, host and client were 32bit stable Gentoo Linux.
>
>
> 6286ae97d10ea2b5cd90532163797ab217bfdbdf is the first bad commit
> commit 6286ae97d10ea2b5cd90532163797ab217bfdbdf
> Author: Christoph Lameter <cl@linux.com>
> Date:   Fri May 3 15:43:18 2013 +0000
>
>     slab: Return NULL for oversized allocations
>
>     The inline path seems to have changed the SLAB behavior for very large
>     kmalloc allocations with  commit e3366016 ("slab: Use common
>     kmalloc_index/kmalloc_size functions"). This patch restores the old
>     behavior but also adds diagnostics so that we can figure where in the
>     code these large allocations occur.
>
>     Reported-and-tested-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
>     Signed-off-by: Christoph Lameter <cl@linux.com>
>     Link: http://lkml.kernel.org/r/201305040348.CIF81716.OStQOHFJMFLOVF@I-love.SAKURA.ne.jp
>     [ penberg@kernel.org: use WARN_ON_ONCE ]
>     Signed-off-by: Pekka Enberg <penberg@kernel.org>
>

So, we trigger "if (WARN_ON_ONCE(size > KMALLOC_MAX_SIZE))".
Now I'm wondering what kind of argument string trinity gave to mount().
How long is it?

BTW: Toralf, why are you sending this to user-mode-linux-*user*@lists...?
We also have a -devel list. Please at least CC me.
Otherwise it is most likely that I miss such reports...

--
Thanks,
//richard

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