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From: Christian Brauner <christian.brauner@ubuntu.com>
To: Michael Ellerman <mpe@ellerman.id.au>
Cc: cyphar@cyphar.com, mingo@redhat.com, peterz@infradead.org,
	alexander.shishkin@linux.intel.com, jolsa@redhat.com,
	namhyung@kernel.org, christian@brauner.io, keescook@chromium.org,
	linux@rasmusvillemoes.dk, viro@zeniv.linux.org.uk,
	torvalds@linux-foundation.org, linux-api@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] usercopy: Avoid soft lockups in test_check_nonzero_user()
Date: Thu, 17 Oct 2019 08:09:39 +0200	[thread overview]
Message-ID: <20191017060938.p4tmr5ruv6frgse4@wittgenstein> (raw)
In-Reply-To: <871rvctkof.fsf@mpe.ellerman.id.au>

On Thu, Oct 17, 2019 at 09:00:48AM +1100, Michael Ellerman wrote:
> Christian Brauner <christian.brauner@ubuntu.com> writes:
> > On Wed, Oct 16, 2019 at 11:27:32PM +1100, Michael Ellerman wrote:
> >> On a machine with a 64K PAGE_SIZE, the nested for loops in
> >> test_check_nonzero_user() can lead to soft lockups, eg:
> >> 
> >>   watchdog: BUG: soft lockup - CPU#4 stuck for 22s! [modprobe:611]
> >>   Modules linked in: test_user_copy(+) vmx_crypto gf128mul crc32c_vpmsum virtio_balloon ip_tables x_tables autofs4
> >>   CPU: 4 PID: 611 Comm: modprobe Tainted: G             L    5.4.0-rc1-gcc-8.2.0-00001-gf5a1a536fa14-dirty #1151
> >>   ...
> >>   NIP __might_sleep+0x20/0xc0
> >>   LR  __might_fault+0x40/0x60
> >>   Call Trace:
> >>     check_zeroed_user+0x12c/0x200
> >>     test_user_copy_init+0x67c/0x1210 [test_user_copy]
> >>     do_one_initcall+0x60/0x340
> >>     do_init_module+0x7c/0x2f0
> >>     load_module+0x2d94/0x30e0
> >>     __do_sys_finit_module+0xc8/0x150
> >>     system_call+0x5c/0x68
> >> 
> >> Even with a 4K PAGE_SIZE the test takes multiple seconds. Instead
> >> tweak it to only scan a 1024 byte region, but make it cross the
> >> page boundary.
> >> 
> >> Fixes: f5a1a536fa14 ("lib: introduce copy_struct_from_user() helper")
> >> Suggested-by: Aleksa Sarai <cyphar@cyphar.com>
> >> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
> >
> > With Aleksa's Reviewed-by I've picked this up:
> > https://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux.git/log/?h=copy_struct_from_user
> 
> Thanks. Are you planning to send that to Linus for v5.4 or v5.5 ?

This looks like a pretty straight bugfix to me since it's clearly
causing an issue for you on power so v5.4-rc4 is what I'd aim for. I
just want it to be in linux-next until tomorrow.

Christian

  reply	other threads:[~2019-10-17  6:10 UTC|newest]

Thread overview: 30+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-01  1:10 [PATCH v4 0/4] lib: introduce copy_struct_from_user() helper Aleksa Sarai
2019-10-01  1:10 ` [PATCH v4 1/4] " Aleksa Sarai
2019-10-01  1:58   ` Kees Cook
2019-10-01  2:31     ` Christian Brauner
2019-10-01 16:28       ` Kees Cook
2019-10-10 11:19   ` Michael Ellerman
2019-10-10 11:19     ` Michael Ellerman
2019-10-10 11:40     ` Aleksa Sarai
2019-10-10 16:43       ` Kees Cook
2019-10-11  2:24       ` [PATCH] usercopy: Avoid soft lockups in test_check_nonzero_user() Michael Ellerman
2019-10-11  3:48         ` Aleksa Sarai
2019-10-11  9:43           ` Christian Brauner
2019-10-16 12:28             ` Michael Ellerman
2019-10-16 12:45               ` Christian Brauner
2019-10-12  9:54           ` Michael Ellerman
2019-10-12 10:12             ` Aleksa Sarai
2019-10-16 12:27         ` [PATCH v2] " Michael Ellerman
2019-10-16 12:36           ` Aleksa Sarai
2019-10-16 12:50           ` Christian Brauner
2019-10-16 13:03           ` Christian Brauner
2019-10-16 22:00             ` Michael Ellerman
2019-10-17  6:09               ` Christian Brauner [this message]
2019-10-23  2:23                 ` Michael Ellerman
2019-10-01  1:10 ` [PATCH v4 2/4] clone3: switch to copy_struct_from_user() Aleksa Sarai
2019-10-01  2:32   ` Christian Brauner
2019-10-01  1:10 ` [PATCH v4 3/4] sched_setattr: " Aleksa Sarai
2019-10-01  2:33   ` Christian Brauner
2019-10-01  1:10 ` [PATCH v4 4/4] perf_event_open: " Aleksa Sarai
2019-10-01  2:36   ` Christian Brauner
2019-10-01 16:01 ` [PATCH v4 0/4] lib: introduce copy_struct_from_user() helper Christian Brauner

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