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Donenfeld" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, John Ogness , Alexander Potapenko , Marco Elver , Dmitry Vyukov , Geert Uytterhoeven , Geert Uytterhoeven Subject: Re: [PATCH v2] mm/kfence: select random number before taking raw lock Message-ID: References: <20220609123319.17576-1-Jason@zx2c4.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220609123319.17576-1-Jason@zx2c4.com> ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1654779174; a=rsa-sha256; cv=none; b=j+934ZEPao489TvruisoUnAYUKTbFTa0pD237nOse2/DPaNbfjUrdmHPosEQ7/r+amA4Z4 YXic8X1CWs9DuH9Hn1byqZkZaCXSj4Cd7ONRH2NXvdsRe63mdQH0o6nqhNJZJHz/KclRBq LF/PEyfzInjSOBijwAjJ3X6PJZtYACc= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=hn7rTMy0; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf18.hostedemail.com: domain of pmladek@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=pmladek@suse.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1654779174; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=gAVJbG/BIIN8NJYQzbcQF6blONkojsp0TRzSyE1rwgY=; b=PhupshvGZTWevhNDTOujY/YZV+krbazOo8/QNe3ulHwbRQlwwyPC/oUjKkZUeoetQ2fqXs TDR/wsUuioGKBjMlCK5TQDZTlnfaDiANRXwbjolUvoBHxl/4qOwOnLMGvHR8X21DNHeOxP wBfYPVo9KIIrVdCZm0zzR/qpo2NDKbA= X-Stat-Signature: 8xcor5jkfhzjaemkttrpmgrkuqg9gdj6 X-Rspam-User: X-Rspamd-Queue-Id: C9EBA1C006C X-Rspamd-Server: rspam07 Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=suse.com header.s=susede1 header.b=hn7rTMy0; dmarc=pass (policy=quarantine) header.from=suse.com; spf=pass (imf18.hostedemail.com: domain of pmladek@suse.com designates 195.135.220.28 as permitted sender) smtp.mailfrom=pmladek@suse.com X-HE-Tag: 1654779173-48366 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu 2022-06-09 14:33:19, Jason A. Donenfeld 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 > Cc: Alexander Potapenko > Cc: Marco Elver > Cc: Dmitry Vyukov > Reported-by: Geert Uytterhoeven > Tested-by: Geert Uytterhoeven > Signed-off-by: Jason A. Donenfeld Reviewed-by: Petr Mladek Thanks a lot for fixing this. It is great to know that the printk kthreads were not the culprit here ;-) Best Regards, Petr