From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 85BC8C10F0E for ; Tue, 9 Apr 2019 10:23:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4B9A32084F for ; Tue, 9 Apr 2019 10:23:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726870AbfDIKXA (ORCPT ); Tue, 9 Apr 2019 06:23:00 -0400 Received: from szxga02-in.huawei.com ([45.249.212.188]:2523 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726035AbfDIKXA (ORCPT ); Tue, 9 Apr 2019 06:23:00 -0400 Received: from DGGEMM402-HUB.china.huawei.com (unknown [172.30.72.57]) by Forcepoint Email with ESMTP id D7131201BCA849118941; Tue, 9 Apr 2019 18:22:57 +0800 (CST) Received: from dggeme763-chm.china.huawei.com (10.3.19.109) by DGGEMM402-HUB.china.huawei.com (10.3.20.210) with Microsoft SMTP Server (TLS) id 14.3.408.0; Tue, 9 Apr 2019 18:22:57 +0800 Received: from [10.134.22.195] (10.134.22.195) by dggeme763-chm.china.huawei.com (10.3.19.109) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.1591.10; Tue, 9 Apr 2019 18:22:57 +0800 Subject: Re: [PATCH v3] f2fs: fix to avoid accessing xattr across the boundary To: Randall Huang , , , References: <20190409085308.212682-1-huangrandall@google.com> From: Chao Yu Message-ID: Date: Tue, 9 Apr 2019 18:22:55 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20190409085308.212682-1-huangrandall@google.com> Content-Type: text/plain; charset="utf-8" Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.134.22.195] X-ClientProxiedBy: dggeme709-chm.china.huawei.com (10.1.199.105) To dggeme763-chm.china.huawei.com (10.3.19.109) X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2019/4/9 16:53, Randall Huang wrote: > When we traverse xattr entries via __find_xattr(), > if the raw filesystem content is faked or any hardware failure occurs, > out-of-bound error can be detected by KASAN. > Fix the issue by introducing boundary check. > > [ 38.402878] c7 1827 BUG: KASAN: slab-out-of-bounds in f2fs_getxattr+0x518/0x68c > [ 38.402891] c7 1827 Read of size 4 at addr ffffffc0b6fb35dc by task > [ 38.402935] c7 1827 Call trace: > [ 38.402952] c7 1827 [] dump_backtrace+0x0/0x6bc > [ 38.402966] c7 1827 [] show_stack+0x20/0x2c > [ 38.402981] c7 1827 [] dump_stack+0xfc/0x140 > [ 38.402995] c7 1827 [] print_address_description+0x80/0x2d8 > [ 38.403009] c7 1827 [] kasan_report_error+0x198/0x1fc > [ 38.403022] c7 1827 [] kasan_report_error+0x0/0x1fc > [ 38.403037] c7 1827 [] __asan_load4+0x1b0/0x1b8 > [ 38.403051] c7 1827 [] f2fs_getxattr+0x518/0x68c > [ 38.403066] c7 1827 [] f2fs_xattr_generic_get+0xb0/0xd0 > [ 38.403080] c7 1827 [] __vfs_getxattr+0x1f4/0x1fc > [ 38.403096] c7 1827 [] inode_doinit_with_dentry+0x360/0x938 > [ 38.403109] c7 1827 [] selinux_d_instantiate+0x2c/0x38 > [ 38.403123] c7 1827 [] security_d_instantiate+0x68/0x98 > [ 38.403136] c7 1827 [] d_splice_alias+0x58/0x348 > [ 38.403149] c7 1827 [] f2fs_lookup+0x608/0x774 > [ 38.403163] c7 1827 [] lookup_slow+0x1e0/0x2cc > [ 38.403177] c7 1827 [] walk_component+0x160/0x520 > [ 38.403190] c7 1827 [] path_lookupat+0x110/0x2b4 > [ 38.403203] c7 1827 [] filename_lookup+0x1d8/0x3a8 > [ 38.403216] c7 1827 [] user_path_at_empty+0x54/0x68 > [ 38.403229] c7 1827 [] SyS_getxattr+0xb4/0x18c > [ 38.403241] c7 1827 [] el0_svc_naked+0x34/0x38 > > Bug: 126558260 > > Signed-off-by: Randall Huang > --- > v2: > * return EFAULT if OOB error is detected > > v3: > * fix typo in setxattr() > --- > fs/f2fs/xattr.c | 31 +++++++++++++++++++++++++++---- > 1 file changed, 27 insertions(+), 4 deletions(-) > > diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c > index 848a785abe25..381f14b02a78 100644 > --- a/fs/f2fs/xattr.c > +++ b/fs/f2fs/xattr.c > @@ -202,12 +202,17 @@ static inline const struct xattr_handler *f2fs_xattr_handler(int index) > return handler; > } > > -static struct f2fs_xattr_entry *__find_xattr(void *base_addr, int index, > - size_t len, const char *name) > +static struct f2fs_xattr_entry *__find_xattr(void *base_addr, > + unsigned int max_size, int index, > + size_t len, const char *name) > { > struct f2fs_xattr_entry *entry; > + void *max_addr = base_addr + ENTRY_SIZE(XATTR_ENTRY(base_addr)) + > + max_size - 1; Hi Randall, I think this is not right, I enable noinline_xattr mount option, and add printk to see the status here, it shows __find_xattr, base_addr:ffff8e709ba92000, max_addr:ffff8e709baa131f, max_size:4 ffff8e709baa131f - ffff8e709ba92000 = F31F > > list_for_each_xattr(entry, base_addr) { > + if ((void *)entry + sizeof(__u32) > max_addr) > + return NULL; > if (entry->e_name_index != index) > continue; > if (entry->e_name_len != len) > @@ -301,6 +306,7 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage, > nid_t xnid = F2FS_I(inode)->i_xattr_nid; > unsigned int size = xnid ? VALID_XATTR_BLOCK_SIZE : 0; > unsigned int inline_size = inline_xattr_size(inode); > + unsigned int max_size = inline_size + size + XATTR_PADDING_SIZE; > int err = 0; > > if (!size && !inline_size) > @@ -323,6 +329,7 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage, > *base_size = inline_size; > goto check; > } > + max_size -= inline_size; The cur_addr pointer may point to middle of inline xattr space due to below code? we should consider such case here. if (last_addr) cur_addr = XATTR_HDR(last_addr) - 1; > } > > /* read from xattr node block */ > @@ -330,6 +337,8 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage, > err = read_xattr_block(inode, txattr_addr); > if (err) > goto out; > + > + max_size -= size; We should not shrink max_size after loading xattr block's data. Thanks, > } > > if (last_addr) > @@ -337,7 +346,12 @@ static int lookup_all_xattrs(struct inode *inode, struct page *ipage, > else > cur_addr = txattr_addr; > > - *xe = __find_xattr(cur_addr, index, len, name); > + *xe = __find_xattr(cur_addr, max_size, index, len, name); > + if (!*xe) { > + err = -EFAULT; > + goto out; > + } > + > check: > if (IS_XATTR_LAST_ENTRY(*xe)) { > err = -ENODATA; > @@ -585,6 +599,11 @@ static int __f2fs_setxattr(struct inode *inode, int index, > int found, newsize; > size_t len; > __u32 new_hsize; > + nid_t xnid = F2FS_I(inode)->i_xattr_nid; > + unsigned int xattr_nid_size = xnid ? VALID_XATTR_BLOCK_SIZE : 0; > + unsigned int inline_size = inline_xattr_size(inode); > + unsigned int max_size = inline_size + xattr_nid_size + > + XATTR_PADDING_SIZE; > int error = 0; > > if (name == NULL) > @@ -606,7 +625,11 @@ static int __f2fs_setxattr(struct inode *inode, int index, > return error; > > /* find entry with wanted name. */ > - here = __find_xattr(base_addr, index, len, name); > + here = __find_xattr(base_addr, max_size, index, len, name); > + if (!here) { > + error = -EFAULT; > + goto exit; > + } > > found = IS_XATTR_LAST_ENTRY(here) ? 0 : 1; > >