From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 8BDCB438012 for ; Fri, 31 Jul 2026 17:35:27 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785519329; cv=none; b=ZBsr4dbOJ4xeC71JvadXyvTE6jruDxrVGlaipMXrLIqCnO0RXHSDtUpmUTSRt4S27JLg11GN9tc7ysy8GbwRhmRT1GbNoC43jaaP1e10GTkXeqXeo1qA/L65lS0YY2/bMx/yFOtxM9f7EmTjmyOJh3vlz06SOiZHaEIQ3FJDDaE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785519329; c=relaxed/simple; bh=Sm4xaDnkjKmdp3Nx5hEXLVClH6n6C9X/Dn2I9wabZ+o=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=iyas/oRmjLeRm+zYjcw+zy/93f0AjCyjk8Qr6N7BdULaCHGndcqiVQkGUu1/i4vb9/D3eixiq0vXGKXGtPn5+3zIG9JZRADBihcwFF9zbyk1D9jjBTODKtl9gQhD7+dcAyymWFszgovmdyoBKZNTxrnbL7efpuSEq+hz81bVffE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=bI5gs6Hw; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="bI5gs6Hw" Received: by smtp.kernel.org (Postfix) with ESMTPSA id AF2811F00AC4; Fri, 31 Jul 2026 17:35:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=korg; t=1785519327; bh=29dpsNY8GA8AuterklDZubYOAzJJs2VhVRhEfB9xQv4=; h=Date:From:To:Cc:Subject:In-Reply-To:References; b=bI5gs6HwjhuHGjQmBYcRTP/mbePYlOW8IP3AjpSVpudyX4lF6ygrcLxY4Jmyturby Hu7NSwhUQaCvFH+Wz6Y267moehckokn3VxxCmOM+t6ucPdbdMrDWs4YscK4HiXB1Od iBhLH2UfVOhCcQeSTIOuRpv7TpBGfl67M6twB0qk= Date: Fri, 31 Jul 2026 10:35:26 -0700 From: Andrew Morton To: syzbot Cc: bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, linux-kernel@vger.kernel.org, mingo@redhat.com, senozhatsky@chromium.org, syzkaller-bugs@googlegroups.com, tglx@kernel.org, tglx@linutronix.de, x86@kernel.org Subject: Re: [syzbot] [kernel?] WARNING in do_clear_cpu_cap Message-Id: <20260731103526.9b9c02f8b5a95b190b23ee51@linux-foundation.org> In-Reply-To: <6a6cd7be.1aa927e4.17d4bf.0005.GAE@google.com> References: <6a6cd7be.1aa927e4.17d4bf.0005.GAE@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 31 Jul 2026 10:13:34 -0700 syzbot wrote: > syzbot found the following issue on: > > HEAD commit: 11028ab62899 Merge tag 'probes-fixes-v7.2-rc5' of git://gi.. > git tree: upstream > console+strace: https://syzkaller.appspot.com/x/log.txt?x=14e3d9b9580000 > kernel config: https://syzkaller.appspot.com/x/.config?x=cb17729fb04b1e3a > dashboard link: https://syzkaller.appspot.com/bug?extid=6cdbd5e494b199d820c3 > compiler: Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8 > syz repro: https://syzkaller.appspot.com/x/repro.syz?x=13b271b9580000 > C reproducer: https://syzkaller.appspot.com/x/repro.c?x=118a97b1580000 > > Downloadable assets: > disk image: https://storage.googleapis.com/syzbot-assets/bc967be819a3/disk-11028ab6.raw.xz > vmlinux: https://storage.googleapis.com/syzbot-assets/6e9f003c9cc8/vmlinux-11028ab6.xz > kernel image: https://storage.googleapis.com/syzbot-assets/5c292926486f/bzImage-11028ab6.xz > > The issue was bisected to: > > commit 684826f8271ad97580b138b9ffd462005e470b99 > Author: Sergey Senozhatsky > Date: Wed Sep 11 02:54:56 2024 +0000 > > zram: free secondary algorithms names Thanks. I don't see how zram could have caused this. fwiw (which might not be a lot), Gemini concluded Core Issue & Summary Root Cause: CPU capability clearing (clear_cpu_cap / setup_clear_cpu_cap) was executed during late CPU feature detection on a secondary core (identify_secondary_cpu()) after kernel alternatives patching was finalized (alternatives_patched == true). Fix Location: The bug needs to be addressed in arch/x86/kernel/cpu/intel.c (specifically around early_init_intel()) by ensuring that capability overrides/clears are done prior to alternative patching or handled via per-CPU feature suppression mechanisms that don't invoke full feature mask clearing post-patching. https://gemini.google.com/share/0cdd1930799f?skid=006fb41e-8e42-4330-9f52-62c4cf089ce0