From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 181E026159C for ; Tue, 8 Apr 2025 09:07:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744103276; cv=none; b=RI/cVNGEiSRt3IOfB3wBElm+zkWSA6Y6pd4MdWQvFDeG637I7lEuIsQbXD8LiiM18oVIpigwsqZkcmGEK68AghIccpFexXPuENgjN9PPJ3exUtrgP/vT5J6PHMsEnT/mUDM0kEq7Zg8XpgqsSG6YGB10W71KJj1zLrWDV6e0xbc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744103276; c=relaxed/simple; bh=21yDSWrTWmTmYJcf09cV8sZWJscX7IffFCn4r+16gLs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=CIMWLfXFe/Isp9ls6LixeIE6iq33vyGhKPZUO5OHJPTEyA0blwzQynf20WdFvvE/o50CEovxpNb/ZANi8mUl1EYpJNrQbFfRbUSkByVb27xxzpl8KFr3b6k1YVDIzoQeRneBi0MGdF1LOZWdA7IAzyKmdJq9VTIB7LJCO6EJhgA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=CAXM18RF; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="CAXM18RF" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB534C4CEE5; Tue, 8 Apr 2025 09:07:53 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1744103274; bh=21yDSWrTWmTmYJcf09cV8sZWJscX7IffFCn4r+16gLs=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CAXM18RFGAcwMtIY5JMqcOhjJ3sI4iWQZmVVahlv82RB9RHNT0RAxtVp6cxr4eVI+ eKnV5Fx8Xnnl34BaPlGIdPLuUX+/i6HzFmB0pCg6tGUMoPM4y2ke1NfEAds9Ayv/sx r7BN1dxZl2wgAPF2MsHeQkVQ+jaL+PuBCEZrCTT4= Date: Tue, 8 Apr 2025 11:06:20 +0200 From: Greg KH To: Kang Wenlin Cc: stable@vger.kernel.org, viro@zeniv.linux.org.uk, brauner@kernel.org, ebiederm@xmission.com, keescook@chromium.org, akpm@linux-foundation.org Subject: Re: [PATCH 6.6.y 0/6] Backported patches to fix selftest tpdir2 Message-ID: <2025040819-unabashed-maximum-8fc8@gregkh> References: <20250402082656.4177277-1-wenlin.kang@windriver.com> <2025040344-coma-strict-4e8f@gregkh> <17b170ac-aa20-4c36-a045-25d2f82e66d0@windriver.com> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <17b170ac-aa20-4c36-a045-25d2f82e66d0@windriver.com> On Fri, Apr 04, 2025 at 03:58:36PM +0800, Kang Wenlin wrote: > Hi Greg > > Thanks for your response. > > > On 4/3/2025 22:52, Greg KH wrote: > > CAUTION: This email comes from a non Wind River email account! > > Do not click links or open attachments unless you recognize the sender and know the content is safe. > > > > On Wed, Apr 02, 2025 at 04:26:50PM +0800, Kang Wenlin wrote: > > > From: Wenlin Kang > > > > > > The selftest tpdir2 terminated with a 'Segmentation fault' during loading. > > > > > > root@localhost:~# cd linux-kenel/tools/testing/selftests/arm64/abi && make > > > root@localhost:~/linux-kernel/tools/testing/selftests/arm64/abi# ./tpidr2 > > > Segmentation fault > > > > > > The cause of this is the __arch_clear_user() failure. > > > > > > load_elf_binary() [fs/binfmt_elf.c] > > > -> if (likely(elf_bss != elf_brk) && unlikely(padzero(elf_bes))) > > > -> padzero() > > > -> clear_user() [arch/arm64/include/asm/uaccess.h] > > > -> __arch_clear_user() [arch/arm64/lib/clear_user.S] > > > > > > For more details, please see: > > > https://lore.kernel.org/lkml/1d0342f3-0474-482b-b6db-81ca7820a462@t-8ch.de/T/ > > This is just a userspace issue (i.e. don't do that, and if you do want > > to do that, use a new kernel!) > > > > Why do these changes need to be backported, do you have real users that > > are crashing in this way to require these changes? > > > This issue was identified during our internal testing, and I found > similar cases discussed in the link above. Upon reviewing the kernel > code, I noticed that a patch series already accepted into mainline > addresses this problem. Since these patches are already upstream > and effectively resolve the issue, I decided to backport them. > We believe this provides a more robust and maintainable solution > compared to relying on users to avoid the triggering behavior. Fixing something just to get the selftests to pass is fine, but do you actually know of a real-world case where this is a problem that needs to be resolved? That's what I'm asking here, do you have users that have run into this issue? I ask as it's not a regression from what I can determine, but rather a new "feature". thanks, greg k-h