From: Geert Uytterhoeven <geert@linux-m68k.org>
To: "Jason A. Donenfeld" <Jason@zx2c4.com>
Cc: Linux MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
John Ogness <john.ogness@linutronix.de>,
Alexander Potapenko <glider@google.com>,
Marco Elver <elver@google.com>,
Dmitry Vyukov <dvyukov@google.com>
Subject: Re: [PATCH] mm/kfence: select random number before taking raw lock
Date: Thu, 9 Jun 2022 14:31:18 +0200 [thread overview]
Message-ID: <CAMuHMdXocvPDViVHjEfeWGxA+7SwOrD3pP7v8wFM80Us3xSU4Q@mail.gmail.com> (raw)
In-Reply-To: <20220609121709.12939-1-Jason@zx2c4.com>
Hi Jason,
On Thu, Jun 9, 2022 at 2:17 PM Jason A. Donenfeld <Jason@zx2c4.com> wrote:
> The RNG uses vanilla spinlocks, not raw spinlocks, so kfence should pick
> its random numbers before taking its raw spinlocks. This also has the
> nice effect of doing less work inside the lock. It should fix a splat
> that Geert saw with CONFIG_PROVE_RAW_LOCK_NESTING:
>
> dump_backtrace.part.0+0x98/0xc0
> show_stack+0x14/0x28
> dump_stack_lvl+0xac/0xec
> dump_stack+0x14/0x2c
> __lock_acquire+0x388/0x10a0
> lock_acquire+0x190/0x2c0
> _raw_spin_lock_irqsave+0x6c/0x94
> crng_make_state+0x148/0x1e4
> _get_random_bytes.part.0+0x4c/0xe8
> get_random_u32+0x4c/0x140
> __kfence_alloc+0x460/0x5c4
> kmem_cache_alloc_trace+0x194/0x1dc
> __kthread_create_on_node+0x5c/0x1a8
> kthread_create_on_node+0x58/0x7c
> printk_start_kthread.part.0+0x34/0xa8
> printk_activate_kthreads+0x4c/0x54
> do_one_initcall+0xec/0x278
> kernel_init_freeable+0x11c/0x214
> kernel_init+0x24/0x124
> ret_from_fork+0x10/0x20
>
> Cc: John Ogness <john.ogness@linutronix.de>
> Cc: Alexander Potapenko <glider@google.com>
> Cc: Marco Elver <elver@google.com>
> Cc: Dmitry Vyukov <dvyukov@google.com>
> Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
> Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Thank you, the splat is gone.
Tested-by: Geert Uytterhoeven <geert+renesas@glider.be>
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
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
prev parent reply other threads:[~2022-06-09 12:31 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-06-09 12:17 Jason A. Donenfeld
2022-06-09 12:27 ` Marco Elver
2022-06-09 12:29 ` Jason A. Donenfeld
2022-06-09 12:33 ` [PATCH v2] " Jason A. Donenfeld
2022-06-09 12:41 ` Marco Elver
2022-06-09 12:52 ` Petr Mladek
2022-06-09 12:31 ` Geert Uytterhoeven [this message]
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