From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 97E9162E for ; Tue, 1 Nov 2022 08:21:49 +0000 (UTC) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id AF0DF1FE4D; Tue, 1 Nov 2022 08:21:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1667290901; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=CwmF+GF8TFJ1DJcjepgRHGxKQmBCUwUcD5eX9NLO3jQ=; b=qvWgpbe/emohvXjwWNSBIyY5uNizh9A+X2Y/scGu9wtK6upAfM+ySEtC2zqYtbswgxG+hm tqHn2snnoRvpFtOi+InpK6dZvkE+HMtKRWLypjWWXJLYmHHKpUu+VXHey01825DdUzmOou 29v0DuUskqHeaXByLr7f7bnHPQW6vx0= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1667290901; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=CwmF+GF8TFJ1DJcjepgRHGxKQmBCUwUcD5eX9NLO3jQ=; b=8yBk+eGkgjLrqU3GH/7ug0JKi1BAZP3oLqWWN5VQESCK6/HveEoDb9p/WzezT1OA4Gsde+ gAsQHSjLIkiAGeCw== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 794911346F; Tue, 1 Nov 2022 08:21:41 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id xp6pHBXXYGMaIQAAMHmgww (envelope-from ); Tue, 01 Nov 2022 08:21:41 +0000 Date: Tue, 01 Nov 2022 09:21:41 +0100 Message-ID: <871qqn84q2.wl-tiwai@suse.de> From: Takashi Iwai To: Steven Rostedt Cc: Takashi Iwai , regressions@lists.linux.dev, linux-kernel@vger.kernel.org, postix@posteo.eu Subject: Re: [REGRESSION 6.0.x / 6.1.x] NULL dereferencing at tracing In-Reply-To: <20221031144850.5522b036@rorschach.local.home> References: <87h6zklb6n.wl-tiwai@suse.de> <20221031144850.5522b036@rorschach.local.home> User-Agent: Wanderlust/2.15.9 (Almost Unreal) Emacs/27.2 Mule/6.0 Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII On Mon, 31 Oct 2022 19:48:50 +0100, Steven Rostedt wrote: > > On Mon, 31 Oct 2022 08:11:28 +0100 > Takashi Iwai wrote: > > > Hi Steven, > > > > we've got a bug report indicating the NULL dereference at the recent > > tracing changes, showing at the start of KDE. The details including > > the dmesg are found at: > > https://bugzilla.opensuse.org/show_bug.cgi?id=1204705 > > > > It was reported at first for 6.0.3, and confirmed that the problem > > persists with 6.1-rc, too. > > > > The culprit seems to be the commit > > f3ddb74ad0790030c9592229fb14d8c451f4e9a8 > > tracing: Wake up ring buffer waiters on closing of the file > > and reverting it seems fixing the problem. > > > > Could you take a look? > > > > > > Can you apply this to see if it fixes it? > > I'm guessing there's a path to the release of the file descriptor where > the ring buffer isn't allocated (and this expected it to be). > > I'll investigate further to see if I can find that path. For avoiding confusion: the follow up post in this thread https://lore.kernel.org/71829e56-a13f-0462-37a7-a4d64c16f561@posteo.de is from Alex, who is the original bug reporter on openSUSE Bugzilla. The test result looks negative, unfortunately. Takashi > > -- Steve > > diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c > index 199759c73519..c1c7ce4c6ddb 100644 > --- a/kernel/trace/ring_buffer.c > +++ b/kernel/trace/ring_buffer.c > @@ -937,6 +937,9 @@ void ring_buffer_wake_waiters(struct trace_buffer *buffer, int cpu) > struct ring_buffer_per_cpu *cpu_buffer; > struct rb_irq_work *rbwork; > > + if (!buffer) > + return; > + > if (cpu == RING_BUFFER_ALL_CPUS) { > > /* Wake up individual ones too. One level recursion */ >