From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp153-165.sina.com.cn (smtp153-165.sina.com.cn [61.135.153.165]) (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 5C0AA1448E0 for ; Thu, 17 Sep 2026 04:24:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=61.135.153.165 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789619055; cv=none; b=eHZzVWMDzbRWuebp2Viicd/ftS+F/Vp70YzZSvN92tOXdu/Xir6/1GiJ0D76vu+pw4WWOCgzeCb0b6Y4P419vw8wd4df8IYZSBRg9RIKnNcNPlMfx7sl293gR8obOsNm3YedLA7mFCmlnILBk+3Ekj12JssDzp9yGaFPxXQ2l0k= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789619055; c=relaxed/simple; bh=NCd1M4BYCsVVcnfJn7CPMrWRew8MFVBraGEWWKIOQSU=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=kIqN8nUnry+hFZ/7O/o96522c9ty4jkn7QMksgMNOqaOIEl7V8cD1/1sSZlmZBAVl1AWbm8hfLczp6Lo8IEOoJOsP5NOQ3CTE1zq/SUshkR61cZCE5h/ccXiTKm0dF+y3cl9SywuqifJLZX/kMcsgU0oj4/GpFTciG29Ts9UvaY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.com; spf=pass smtp.mailfrom=sina.com; dkim=pass (1024-bit key) header.d=sina.com header.i=@sina.com header.b=nLH2jIVG; arc=none smtp.client-ip=61.135.153.165 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=sina.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=sina.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=sina.com header.i=@sina.com header.b="nLH2jIVG" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sina.com; s=201208; t=1789619047; bh=XIDlTScOG9QnL6L081k6czMCkrQnIa7NpQIs6PMtKVY=; h=From:Subject:Date:Message-ID; b=nLH2jIVGCQ3BkuqYGINz365Ebzue6NSdhMYOj2xoZvauys4BrClUP+JQDKOaip5pL AF7c6CCP3ljFdTSFGIPhqZGap2XFoe93UTJ/1mt1qyfzT+mi08ZfWWOo2T1fq04xKV I/Gr3ErMqlFnfkyC1Mq+cNNKlsmGXldYXaz0s6Bw= X-SMAIL-HELO: lxu-ped-host.. Received: from unknown (HELO lxu-ped-host..)([111.198.231.89]) by sina.com (10.54.253.32) with ESMTP id 6AAB6B6000003938; Thu, 17 Sep 2026 12:24:02 +0800 (CST) X-Sender: eadavis@sina.com X-Auth-ID: eadavis@sina.com Authentication-Results: sina.com; spf=none smtp.mailfrom=eadavis@sina.com; dkim=none header.i=none; dmarc=none action=none header.from=eadavis@sina.com X-SMAIL-MID: 9779204456617 X-SMAIL-UIID: BC0889522A6D4250A62018007C6511F2-20260917-122402-1 From: Edward Adam Davis To: gregkh@linuxfoundation.org Cc: dakr@kernel.org, driver-core@lists.linux.dev, eadavis@sina.com, linux-kernel@vger.kernel.org, rafael@kernel.org, syzbot+9a321aea9d851b299486@syzkaller.appspotmail.com, syzkaller-bugs@googlegroups.com Subject: Re: [PATCH] sysfs: prevent writing excessively large files Date: Thu, 17 Sep 2026 12:24:00 +0800 Message-ID: <20260917042400.985424-1-eadavis@sina.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <2026091641-tanned-bust-37f2@gregkh> References: <2026091641-tanned-bust-37f2@gregkh> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Edward Aadm Davis On Wed, 16 Sep 2026 18:44:06 +0100, Greg KH wrote: > On Wed, Sep 16, 2026 at 06:19:30PM +0800, Edward Adam Davis wrote: > > From: Edward Aadm Davis > > > > On Wed, 16 Sep 2026 09:17:56 +0200, Greg KH wrote: > > > > Since atomic_write_len is not configured for sysfs_file_kfops_rw, a large > > > > file write via sysfs_kf_write() may result in an out-of-bounds read when > > > > checking for the null terminator of a string element in the kobject_actions > > > > array within kobject_action_type(), potentially hitting: > > > > > > What sysfs file are you hitting this on? > > Regular sysfs files. > > Which one, all? /sys/bus/acpi/uevent > > > > > BUG: KASAN: global-out-of-bounds in kobject_action_type lib/kobject_uevent.c:86 [inline] > > > > BUG: KASAN: global-out-of-bounds in kobject_synth_uevent+0x79d/0x7d0 lib/kobject_uevent.c:200 > > > > Read of size 1 at addr ffffffff8d72559f by task syz.0.17/5917 > > > > Call Trace: > > > > kobject_action_type lib/kobject_uevent.c:86 [inline] > > > > kobject_synth_uevent+0x79d/0x7d0 lib/kobject_uevent.c:200 > > > > bus_uevent_store+0x3d/0x90 drivers/base/bus.c:917 > > > > bus_attr_store+0x74/0xb0 drivers/base/bus.c:172 > > > > sysfs_kf_write+0xf2/0x150 fs/sysfs/file.c:145 > > > > kernfs_fop_write_iter+0x3e0/0x5f0 fs/kernfs/file.c:345 > > > > new_sync_write fs/read_write.c:595 [inline] > > > > vfs_write+0x6af/0x1050 fs/read_write.c:687 > > > > > > > > Add atomic_write_len for sysfs_file_kfops_rw and sysfs_file_kfops_wo > > > > properly. > > > > > > > > Fixes: f6acf8bb6a40 ("sysfs, kernfs: introduce kernfs_ops") > > > > > > What changed to suddenly cause this to show up now if this has been > > > present for decades? > > This issue has always existed. It remained undetected simply because the > > buffer lengths typically passed when writing to `/sys/bus/acpi/uevent` > > happened to be reasonably appropriate. > > So what changed to cause this to show up now? Starting from f6acf8bb6a40. cheers, Edward