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=-5.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 96B14C43141 for ; Thu, 14 Nov 2019 19:55:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7066E2072E for ; Thu, 14 Nov 2019 19:55:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="key not found in DNS" (0-bit key) header.d=szeredi.hu header.i=@szeredi.hu header.b="BFYdVXTb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726474AbfKNTzx (ORCPT ); Thu, 14 Nov 2019 14:55:53 -0500 Received: from mail-wr1-f65.google.com ([209.85.221.65]:37086 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726491AbfKNTzw (ORCPT ); Thu, 14 Nov 2019 14:55:52 -0500 Received: by mail-wr1-f65.google.com with SMTP id t1so8061933wrv.4 for ; Thu, 14 Nov 2019 11:55:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=szeredi.hu; s=google; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=wcxBRQ29xnxU5Y9UL6AGFLVVPVxLVFbf1Hf8+WtVO5g=; b=BFYdVXTbKRu/m+SMcQPoHqwbwI3pNa9TjwMMYmZicmPXGCHifINOCFQZzQQjDIKOd0 /QTZBU/aMn3c5ICHlnrSIQ0mkrULDIqpLjh+mBuA3eaNEaDh+7ztxDvk3RR51FjTZgcc MSPCO2RQbEg5GK39QqqpWulMZm8aUQykJR//8= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=wcxBRQ29xnxU5Y9UL6AGFLVVPVxLVFbf1Hf8+WtVO5g=; b=feazMCGRv1sypv5uFSiFCR04qRPH96mPVgZNw9fzTnkqoYB9stvrNgB3dLX9vRohRn xzOxPskJVoL8JzJvYuQbb13PbVHRgxOiBEo+ez0JUeLbCI+FWswX4C8pKmHwVC4GaiFN k+kFDa7EM9J54EZ133CVACHN2j8XOBuDzC1cb+PHYOPyjFVxukoZTHAzqkKI67RhNEnB DsOWRX+bvHPx5Cn1gtlnKnEdKPAg2IdW27+1EbVwHAEMkEAi+4vu9Yuzt6MB7Jr38/Je O4aPStSZrB1qA9NYT9b/0AxrWrRs1LZmYMkjSwkbF4sS86Du2ZR/iXb0gv/siAGEBVrH qQVw== X-Gm-Message-State: APjAAAXdsEgioak2t4nDLlZzBN1IojET2clPUy/O/fWYVK5J0hqm8x3z O+h/g7zpgZzEKcUr1ZTmeMHh+g== X-Google-Smtp-Source: APXvYqyab/oIRJv3swgEHrQbrEGDk75slT7tgN4sXu3Q2k/eZY8ehb5fHbGHbaM034xwf+rX9tuGTQ== X-Received: by 2002:a5d:4e89:: with SMTP id e9mr11030822wru.342.1573761347793; Thu, 14 Nov 2019 11:55:47 -0800 (PST) Received: from miu.piliscsaba.redhat.com (catv-212-96-48-140.catv.broadband.hu. [212.96.48.140]) by smtp.gmail.com with ESMTPSA id g5sm7916089wmf.37.2019.11.14.11.55.46 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 Nov 2019 11:55:46 -0800 (PST) Date: Thu, 14 Nov 2019 20:55:44 +0100 From: Miklos Szeredi To: Al Viro Cc: Amir Goldstein , linux-fsdevel@vger.kernel.org, linux-nfs@vger.kernel.org, "J. Bruce Fields" Subject: Re: [RFC] is ovl_fh->fid really intended to be misaligned? Message-ID: <20191114195544.GB5569@miu.piliscsaba.redhat.com> References: <20191114154723.GJ26530@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191114154723.GJ26530@ZenIV.linux.org.uk> User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-nfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org On Thu, Nov 14, 2019 at 03:47:23PM +0000, Al Viro wrote: > AFAICS, this > bytes = (fh->len - offsetof(struct ovl_fh, fid)); > real = exportfs_decode_fh(mnt, (struct fid *)fh->fid, > bytes >> 2, (int)fh->type, > connected ? ovl_acceptable : NULL, mnt); > in ovl_decode_real_fh() combined with > origin = ovl_decode_real_fh(fh, ofs->lower_layers[i].mnt, > connected); > in ovl_check_origin_fh(), > /* First lookup overlay inode in inode cache by origin fh */ > err = ovl_check_origin_fh(ofs, fh, false, NULL, &stack); > in ovl_lower_fh_to_d() and > struct ovl_fh *fh = (struct ovl_fh *) fid; > ... > ovl_lower_fh_to_d(sb, fh); > in ovl_fh_to_dentry() leads to the pointer to struct fid passed to > exportfs_decode_fh() being 21 bytes ahead of that passed to > ovl_fh_to_dentry(). > > However, alignment of struct fid pointers is 32 bits and quite a few > places dealing with those (including ->fh_to_dentry() instances) > do access them directly. Argument of ->fh_to_dentry() is supposed > to be 32bit-aligned, and callers generally guarantee that. Your > code, OTOH, violates the alignment systematically there - what > it passes to layers' ->fh_to_dentry() (by way of exportfs_decode_fh()) > always has two lower bits different from what it got itself. > > What do we do with that? One solution would be to insert sane padding > in ovl_fh, but the damn thing appears to be stored as-is in xattrs on > disk, so that would require rather unpleasant operations reinserting > the padding on the fly ;-/ Something like this? Totally untested... Thanks, Miklos diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index b801c6353100..60a4ca72cb4e 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -253,7 +253,7 @@ struct ovl_fh *ovl_encode_real_fh(struct dentry *real, bool is_upper) BUILD_BUG_ON(MAX_HANDLE_SZ + offsetof(struct ovl_fh, fid) > 255); fh_len = offsetof(struct ovl_fh, fid) + buflen; - fh = kmalloc(fh_len, GFP_KERNEL); + fh = kzalloc(fh_len, GFP_KERNEL); if (!fh) { fh = ERR_PTR(-ENOMEM); goto out; @@ -271,7 +271,7 @@ struct ovl_fh *ovl_encode_real_fh(struct dentry *real, bool is_upper) */ if (is_upper) fh->flags |= OVL_FH_FLAG_PATH_UPPER; - fh->len = fh_len; + fh->len = fh_len - OVL_FH_WIRE_OFFSET; fh->uuid = *uuid; memcpy(fh->fid, buf, buflen); @@ -300,7 +300,8 @@ int ovl_set_origin(struct dentry *dentry, struct dentry *lower, /* * Do not fail when upper doesn't support xattrs. */ - err = ovl_check_setxattr(dentry, upper, OVL_XATTR_ORIGIN, fh, + err = ovl_check_setxattr(dentry, upper, OVL_XATTR_ORIGIN, + fh ? OVL_FH_START(fh) : NULL, fh ? fh->len : 0, 0); kfree(fh); @@ -317,7 +318,8 @@ static int ovl_set_upper_fh(struct dentry *upper, struct dentry *index) if (IS_ERR(fh)) return PTR_ERR(fh); - err = ovl_do_setxattr(index, OVL_XATTR_UPPER, fh, fh->len, 0); + err = ovl_do_setxattr(index, OVL_XATTR_UPPER, + OVL_FH_START(fh), fh->len, 0); kfree(fh); return err; diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c index 73c9775215b3..dedda95c7746 100644 --- a/fs/overlayfs/export.c +++ b/fs/overlayfs/export.c @@ -234,7 +234,7 @@ static int ovl_d_to_fh(struct dentry *dentry, char *buf, int buflen) if (fh->len > buflen) goto fail; - memcpy(buf, (char *)fh, fh->len); + memcpy(buf, OVL_FH_START(fh), fh->len); err = fh->len; out: @@ -260,6 +260,7 @@ static int ovl_dentry_to_fh(struct dentry *dentry, u32 *fid, int *max_len) /* Round up to dwords */ *max_len = (len + 3) >> 2; + memset(fid + len, 0, (*max_len << 2) - len); return OVL_FILEID; } @@ -781,7 +782,7 @@ static struct dentry *ovl_fh_to_dentry(struct super_block *sb, struct fid *fid, int fh_len, int fh_type) { struct dentry *dentry = NULL; - struct ovl_fh *fh = (struct ovl_fh *) fid; + struct ovl_fh *fh = (void *) fid - OVL_FH_WIRE_OFFSET; int len = fh_len << 2; unsigned int flags = 0; int err; diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index e9717c2f7d45..f22a65359df1 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -86,7 +86,8 @@ static int ovl_acceptable(void *ctx, struct dentry *dentry) */ int ovl_check_fh_len(struct ovl_fh *fh, int fh_len) { - if (fh_len < sizeof(struct ovl_fh) || fh_len < fh->len) + if (fh_len < sizeof(struct ovl_fh) - OVL_FH_WIRE_OFFSET || + fh_len < fh->len) return -EINVAL; if (fh->magic != OVL_FH_MAGIC) @@ -119,11 +120,11 @@ static struct ovl_fh *ovl_get_fh(struct dentry *dentry, const char *name) if (res == 0) return NULL; - fh = kzalloc(res, GFP_KERNEL); + fh = kzalloc(res + OVL_FH_WIRE_OFFSET, GFP_KERNEL); if (!fh) return ERR_PTR(-ENOMEM); - res = vfs_getxattr(dentry, name, fh, res); + res = vfs_getxattr(dentry, name, fh + OVL_FH_WIRE_OFFSET, res); if (res < 0) goto fail; @@ -161,7 +162,7 @@ struct dentry *ovl_decode_real_fh(struct ovl_fh *fh, struct vfsmount *mnt, if (!uuid_equal(&fh->uuid, &mnt->mnt_sb->s_uuid)) return NULL; - bytes = (fh->len - offsetof(struct ovl_fh, fid)); + bytes = (fh->len + OVL_FH_WIRE_OFFSET - offsetof(struct ovl_fh, fid)); real = exportfs_decode_fh(mnt, (struct fid *)fh->fid, bytes >> 2, (int)fh->type, connected ? ovl_acceptable : NULL, mnt); @@ -433,7 +434,8 @@ int ovl_verify_set_fh(struct dentry *dentry, const char *name, err = ovl_verify_fh(dentry, name, fh); if (set && err == -ENODATA) - err = ovl_do_setxattr(dentry, name, fh, fh->len, 0); + err = ovl_do_setxattr(dentry, name, + OVL_FH_START(fh), fh->len, 0); if (err) goto fail; @@ -512,12 +514,12 @@ int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index) err = -ENOMEM; len = index->d_name.len / 2; - fh = kzalloc(len, GFP_KERNEL); + fh = kzalloc(len + OVL_FH_WIRE_OFFSET, GFP_KERNEL); if (!fh) goto fail; err = -EINVAL; - if (hex2bin((u8 *)fh, index->d_name.name, len)) + if (hex2bin(OVL_FH_START(fh), index->d_name.name, len)) goto fail; err = ovl_check_fh_len(fh, len); @@ -603,7 +605,7 @@ static int ovl_get_index_name_fh(struct ovl_fh *fh, struct qstr *name) if (!n) return -ENOMEM; - s = bin2hex(n, fh, fh->len); + s = bin2hex(n, OVL_FH_START(fh), fh->len); *name = (struct qstr) QSTR_INIT(n, s - n); return 0; diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index 6934bcf030f0..c62083671a12 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -74,8 +74,13 @@ enum ovl_entry_flag { /* The type returned by overlay exportfs ops when encoding an ovl_fh handle */ #define OVL_FILEID 0xfb -/* On-disk and in-memeory format for redirect by file handle */ +#define OVL_FH_WIRE_OFFSET 3 +#define OVL_FH_START(fh) ((void *)(fh) + OVL_FH_WIRE_OFFSET) struct ovl_fh { + /* make sure fid is 32bit aligned */ + u8 padding[OVL_FH_WIRE_OFFSET]; + + /* Wire/xattr encoding begins here*/ u8 version; /* 0 */ u8 magic; /* 0xfb */ u8 len; /* size of this header + size of fid */