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 8B93A433041; Tue, 13 Oct 2026 12:48:31 +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=1791895712; cv=none; b=hzq8carnJ8wtqIkNh3kxYCeg2hJGawvP+RaTWpfuTOAk4O/Oc/WpXffy3JDWmGpkoL22+N2V10DoJMpdPBYOjA8NqoOzbFUqDsoX/Wxaoso3U1qS/5rafYQ15nQUTwFXR8ztIJY+mWQsCMAfbt8StSD+VXbsBN1Ja88c/8lutxU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1791895712; c=relaxed/simple; bh=5PTMk3Vo6VPAvaaFIBTnSZUxGBzWikSg2+TpyTVa+n0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Y3dwtg55us6YaqqUCDTmMyrM5ckgf5yOpboZHc0LasIpuGf1EMoIUYX2NX46Ky0kQqkyS0SwNStv2oMitVQwdq1z1zi/LVQJou561FJreGu1AGyyIMdB3o4jjabG5GFY1+LGeRRGRpQeXluZ9rnBP6mwrKaI9A5DEGUldHMTCpo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=yclONUwX; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="yclONUwX" Received: by smtp.kernel.org (Postfix) with ESMTPSA id DF5711F000FF; Tue, 13 Oct 2026 12:48:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1791895711; bh=kfPG09ZPZQiRljzj5WL5y/uENET7GI6b9/2kLoY/g1M=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=yclONUwXCi1fzI6qi2JCqg59Zn4Sf/uqMsQ9vTtqI4mZKvPF9sBs2/iBM+Jgkljkt k+WVYAVtT/9+cjX/Gz4vD/b5SalIx3LzTDs5Gv41FslR8D/zG40SCoKSAfSTCARKbk XYHWAoWPSRgGeslboZvg3M21ciH7lHMway6NGPa8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, syzbot+48d935cf48a4a76be346@syzkaller.appspotmail.com, Palla Raghunath , Mikulas Patocka Subject: [PATCH 6.12 365/497] dm ioctl: dont let data_start run past the buffer Date: Tue, 13 Oct 2026 13:38:52 +0200 Message-ID: <20261013112916.566595980@linuxfoundation.org> X-Mailer: git-send-email 2.56.0 In-Reply-To: <20261013112907.864180619@linuxfoundation.org> References: <20261013112907.864180619@linuxfoundation.org> User-Agent: quilt/0.69 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 6.12-stable review patch. If anyone has any objections, please let me know. ------------------ From: Palla Raghunath commit 9b3fcf519d370df94a56f3b272d9eddffffa5be8 upstream. struct dm_ioctl has seven bytes of trailing padding, so the smallest buffer userspace is allowed to ask for, offsetof(struct dm_ioctl, data), is seven bytes shorter than sizeof(struct dm_ioctl). get_result_buffer() sets data_start to sizeof(struct dm_ioctl) without looking at how big the buffer actually is. Ask for the minimum and data_start ends up seven bytes past the end. Callers add it to data_size, and ctl_ioctl() copies that much back to userspace: BUG: KASAN: slab-out-of-bounds in _copy_to_user+0xad/0xd0 Read of size 312 at addr ffff8880169e4c00 by task repro-dm/140 ctl_ioctl+0x5e3/0xcb0 dm_ctl_ioctl+0x25/0x40 allocated 305-byte region [ffff8880169e4c00, ffff8880169e4d31) A DM_LIST_DEVICES with data_size set to 305 is enough to hit it, and the seven bytes that leak are whatever sat next to the allocation. Clamp data_start to the buffer size. Note that this is not a security bug because the out-of-bounds read can only be triggered by root. Reported-by: syzbot+48d935cf48a4a76be346@syzkaller.appspotmail.com Closes: https://syzkaller.appspot.com/bug?extid=48d935cf48a4a76be346 Fixes: 76c072b48e39 ("dm ioctl: move compat code") Cc: stable@vger.kernel.org Signed-off-by: Palla Raghunath Signed-off-by: Mikulas Patocka Signed-off-by: Greg Kroah-Hartman --- drivers/md/dm-ioctl.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) --- a/drivers/md/dm-ioctl.c +++ b/drivers/md/dm-ioctl.c @@ -556,10 +556,16 @@ static void *get_result_buffer(struct dm { param->data_start = align_ptr(param + 1) - (void *) param; - if (param->data_start < param_size) + if (param->data_start < param_size) { *len = param_size - param->data_start; - else + } else { + /* + * The buffer can be as small as offsetof(*param, data), which + * is less than sizeof(*param), so don't run off the end of it. + */ *len = 0; + param->data_start = param_size; + } return ((void *) param) + param->data_start; }