From patchwork Tue May 9 19:08:39 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: George Kennedy X-Patchwork-Id: 680470 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DDE17C77B75 for ; Tue, 9 May 2023 19:10:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229966AbjEITKk (ORCPT ); Tue, 9 May 2023 15:10:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44648 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229667AbjEITKf (ORCPT ); Tue, 9 May 2023 15:10:35 -0400 Received: from mx0a-00069f02.pphosted.com (mx0a-00069f02.pphosted.com [205.220.165.32]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8B04340C9; Tue, 9 May 2023 12:10:31 -0700 (PDT) Received: from pps.filterd (m0246617.ppops.net [127.0.0.1]) by mx0b-00069f02.pphosted.com (8.17.1.19/8.17.1.19) with ESMTP id 349ER8Ym002726; Tue, 9 May 2023 19:10:12 GMT DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=oracle.com; h=from : to : cc : subject : date : message-id; s=corp-2023-03-30; bh=ewPY1TNUNNQgf5lnWkZB2J41Mv5DBP76uVt2kOutHyE=; b=DFsTKNcwX3Y9/MFZ//7eKUVjY0YvMazqyJiJDMZDmVCGWOhD25YJPowySiyT0q1aCJjL Fq7QlvHykp/F+mxu735tIQFpsz0hQZ7n1jMUull1sMF2tnPVOa4BOLxe5z7ljXdKV7bS 63WfomRETDyI2UhhHfstMpqqTHAAHyoAfDCHEaaMFIe33KdssHQiPLWM8zvLRu6W3J+i gYHnYogeTugaF/KV13UK8NOPiWsuVurKtnC6oSb3OEadaINCd3WKt09bOgNVB4AmwgCF G0iXfEWF1BaOzinJNmkG9AP/01nos894+qUO3FJ9p3C5nH+g9EgYVxGo1mv9NwRv3mxW bw== Received: from phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta01.appoci.oracle.com [138.1.114.2]) by mx0b-00069f02.pphosted.com (PPS) with ESMTPS id 3qf77c2qp3-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 09 May 2023 19:10:11 +0000 Received: from pps.filterd (phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (8.17.1.19/8.17.1.19) with ESMTP id 349I0qWa002118; Tue, 9 May 2023 19:10:11 GMT Received: from pps.reinject (localhost [127.0.0.1]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTPS id 3qf81eu3en-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Tue, 09 May 2023 19:10:11 +0000 Received: from phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com [127.0.0.1]) by pps.reinject (8.17.1.5/8.17.1.5) with ESMTP id 349J8CFi033427; Tue, 9 May 2023 19:10:10 GMT Received: from gkennedy-linux.us.oracle.com (gkennedy-linux.us.oracle.com [10.152.170.45]) by phxpaimrmta01.imrmtpd1.prodappphxaev1.oraclevcn.com (PPS) with ESMTP id 3qf81eu3de-1; Tue, 09 May 2023 19:10:10 +0000 From: George Kennedy To: gregkh@linuxfoundation.org, jirislaby@kernel.org Cc: george.kennedy@oracle.com, sfr@canb.auug.org.au, akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org, linux@weissschuh.net, regressions@lists.linux.dev Subject: [PATCH] vc_screen: reload load of struct vc_data pointer in vcs_write() to avoid UAF Date: Tue, 9 May 2023 14:08:39 -0500 Message-Id: <1683659319-29701-1-git-send-email-george.kennedy@oracle.com> X-Mailer: git-send-email 1.8.3.1 X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.254,Aquarius:18.0.942,Hydra:6.0.573,FMLib:17.11.170.22 definitions=2023-05-09_12,2023-05-05_01,2023-02-09_01 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 mlxlogscore=999 adultscore=0 mlxscore=0 bulkscore=0 suspectscore=0 malwarescore=0 spamscore=0 phishscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2304280000 definitions=main-2305090158 X-Proofpoint-GUID: j9uN6TZ7areNZWC1Pk6Ho4UONls_fWW5 X-Proofpoint-ORIG-GUID: j9uN6TZ7areNZWC1Pk6Ho4UONls_fWW5 Precedence: bulk List-ID: X-Mailing-List: linux-serial@vger.kernel.org After a call to console_unlock() in vcs_write() the vc_data struct can be freed by vc_port_destruct(). Because of that, the struct vc_data pointer must be reloaded in the while loop in vcs_write() after console_lock() to avoid a UAF when vcs_size() is called. Syzkaller reported a UAF in vcs_size(). BUG: KASAN: slab-use-after-free in vcs_size (drivers/tty/vt/vc_screen.c:215) Read of size 4 at addr ffff8880beab89a8 by task repro_vcs_size/4119 Call Trace: __asan_report_load4_noabort (mm/kasan/report_generic.c:380) vcs_size (drivers/tty/vt/vc_screen.c:215) vcs_write (drivers/tty/vt/vc_screen.c:664) vfs_write (fs/read_write.c:582 fs/read_write.c:564) ... Allocated by task 1213: kmalloc_trace (mm/slab_common.c:1064) vc_allocate (./include/linux/slab.h:559 ./include/linux/slab.h:680 drivers/tty/vt/vt.c:1078 drivers/tty/vt/vt.c:1058) con_install (drivers/tty/vt/vt.c:3334) tty_init_dev (drivers/tty/tty_io.c:1303 drivers/tty/tty_io.c:1415 drivers/tty/tty_io.c:1392) tty_open (drivers/tty/tty_io.c:2082 drivers/tty/tty_io.c:2128) chrdev_open (fs/char_dev.c:415) do_dentry_open (fs/open.c:921) vfs_open (fs/open.c:1052) ... Freed by task 4116: kfree (mm/slab_common.c:1016) vc_port_destruct (drivers/tty/vt/vt.c:1044) tty_port_destructor (drivers/tty/tty_port.c:296) tty_port_put (drivers/tty/tty_port.c:312) vt_disallocate_all (drivers/tty/vt/vt_ioctl.c:662 (discriminator 2)) vt_ioctl (drivers/tty/vt/vt_ioctl.c:903) tty_ioctl (drivers/tty/tty_io.c:2778) ... The buggy address belongs to the object at ffff8880beab8800 which belongs to the cache kmalloc-1k of size 1024 The buggy address is located 424 bytes inside of freed 1024-byte region [ffff8880beab8800, ffff8880beab8c00) The buggy address belongs to the physical page: page:00000000afc77580 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0xbeab8 head:00000000afc77580 order:3 entire_mapcount:0 nr_pages_mapped:0 pincount:0 flags: 0xfffffc0010200(slab|head|node=0|zone=1|lastcpupid=0x1fffff) page_type: 0xffffffff() raw: 000fffffc0010200 ffff888100042dc0 ffffea000426de00 dead000000000002 raw: 0000000000000000 0000000000100010 00000001ffffffff 0000000000000000 page dumped because: kasan: bad access detected Memory state around the buggy address: ffff8880beab8880: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880beab8900: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb >ffff8880beab8980: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ^ ffff8880beab8a00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ffff8880beab8a80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb ================================================================== Disabling lock debugging due to kernel taint Fixes: ac751efa6a0d ("console: rename acquire/release_console_sem() to console_lock/unlock()") Reported-by: syzkaller Signed-off-by: George Kennedy --- This patch is similar to the recent UAF vcs_read() patches (226fae124b2d & 46d733d0efc7). vcs_write() should have been checked for the same UAF issue at the same time the fixes went into vcs_read(). drivers/tty/vt/vc_screen.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-) diff --git a/drivers/tty/vt/vc_screen.c b/drivers/tty/vt/vc_screen.c index 498ba9c0ee93..cbd534a5cead 100644 --- a/drivers/tty/vt/vc_screen.c +++ b/drivers/tty/vt/vc_screen.c @@ -656,10 +656,16 @@ vcs_write(struct file *file, const char __user *buf, size_t count, loff_t *ppos) } } - /* The vcs_size might have changed while we slept to grab - * the user buffer, so recheck. + /* The vc might have been freed or vcs_size might have changed + * while we slept to grab the user buffer, so recheck. * Return data written up to now on failure. */ + vc = vcs_vc(inode, &viewed); + if (!vc) { + if (written) + break; + goto unlock_out; + } size = vcs_size(vc, attr, false); if (size < 0) { if (written)