From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miklos Szeredi Subject: Re: [PATCH v2 03/17] ovl: decode pure upper file handles Date: Thu, 18 Jan 2018 15:09:20 +0100 Message-ID: References: <1515086449-26563-1-git-send-email-amir73il@gmail.com> <1515086449-26563-4-git-send-email-amir73il@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Return-path: In-Reply-To: <1515086449-26563-4-git-send-email-amir73il@gmail.com> Sender: linux-fsdevel-owner@vger.kernel.org To: Amir Goldstein Cc: overlayfs , linux-fsdevel@vger.kernel.org, Al Viro List-Id: linux-unionfs@vger.kernel.org [Added Al Viro] On Thu, Jan 4, 2018 at 6:20 PM, Amir Goldstein wrote: > Decoding an upper file handle is done by decoding the upper dentry from > underlying upper fs, finding or allocating an overlay inode that is > hashed by the real upper inode and instantiating an overlay dentry with > that inode. > > Signed-off-by: Amir Goldstein > --- > fs/overlayfs/export.c | 91 ++++++++++++++++++++++++++++++++++++++++++++++++ > fs/overlayfs/namei.c | 4 +-- > fs/overlayfs/overlayfs.h | 2 ++ > 3 files changed, 95 insertions(+), 2 deletions(-) > > diff --git a/fs/overlayfs/export.c b/fs/overlayfs/export.c > index 58c4f5e8a67e..5c72784a0b4d 100644 > --- a/fs/overlayfs/export.c > +++ b/fs/overlayfs/export.c > @@ -93,6 +93,97 @@ static int ovl_encode_inode_fh(struct inode *inode, u32 *fid, int *max_len, > return type; > } > > +/* > + * Find or instantiate an overlay dentry from real dentries. > + */ > +static struct dentry *ovl_obtain_alias(struct super_block *sb, > + struct dentry *upper, > + struct ovl_path *lowerpath) > +{ > + struct inode *inode; > + struct dentry *dentry; > + struct ovl_entry *oe; > + > + /* TODO: obtain non pure-upper */ > + if (lowerpath) > + return ERR_PTR(-EIO); > + > + inode = ovl_get_inode(sb, dget(upper), NULL, NULL, 0); > + if (IS_ERR(inode)) { > + dput(upper); > + return ERR_CAST(inode); > + } > + > + dentry = d_obtain_alias(inode); > + if (IS_ERR(dentry) || dentry->d_fsdata) Racing two instances of this code, each thinking it got a new alias and trying to fill it, results in a memory leak. Haven't checked in too much depth, but apparently other filesystems are not affected, so we need something special here. One solution: split d_instantiate_anon(dentry, inode) out of __d_obtain_alias() and supply that with the already initialized dentry. Al? Thanks, Miklos > + return dentry; > + > + oe = ovl_alloc_entry(0); > + if (!oe) { > + dput(dentry); > + return ERR_PTR(-ENOMEM); > + } > + > + dentry->d_fsdata = oe; > + ovl_dentry_set_upper_alias(dentry); > + > + return dentry; > +} > + > +static struct dentry *ovl_upper_fh_to_d(struct super_block *sb, > + struct ovl_fh *fh) > +{ > + struct ovl_fs *ofs = sb->s_fs_info; > + struct dentry *dentry; > + struct dentry *upper; > + > + if (!ofs->upper_mnt) > + return ERR_PTR(-EACCES); > + > + upper = ovl_decode_fh(fh, ofs->upper_mnt); > + if (IS_ERR_OR_NULL(upper)) > + return upper; > + > + dentry = ovl_obtain_alias(sb, upper, NULL); > + dput(upper); > + > + return dentry; > +} > + > +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; > + int len = fh_len << 2; > + unsigned int flags = 0; > + int err; > + > + err = -EINVAL; > + if (fh_type != OVL_FILEID) > + goto out_err; > + > + err = ovl_check_fh_len(fh, len); > + if (err) > + goto out_err; > + > + /* TODO: decode non-upper */ > + flags = fh->flags; > + if (flags & OVL_FH_FLAG_PATH_UPPER) > + dentry = ovl_upper_fh_to_d(sb, fh); > + err = PTR_ERR(dentry); > + if (IS_ERR(dentry) && err != -ESTALE) > + goto out_err; > + > + return dentry; > + > +out_err: > + pr_warn_ratelimited("overlayfs: failed to decode file handle (len=%d, type=%d, flags=%x, err=%i)\n", > + len, fh_type, flags, err); > + return ERR_PTR(err); > +} > + > const struct export_operations ovl_export_operations = { > .encode_fh = ovl_encode_inode_fh, > + .fh_to_dentry = ovl_fh_to_dentry, > }; > diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c > index a69cedf06000..87d39384dc55 100644 > --- a/fs/overlayfs/namei.c > +++ b/fs/overlayfs/namei.c > @@ -107,7 +107,7 @@ static int ovl_acceptable(void *ctx, struct dentry *dentry) > * Return -ENODATA for "origin unknown". > * Return <0 for an invalid file handle. > */ > -static int ovl_check_fh_len(struct ovl_fh *fh, int fh_len) > +int ovl_check_fh_len(struct ovl_fh *fh, int fh_len) > { > if (fh_len < sizeof(struct ovl_fh) || fh_len < fh->len) > return -EINVAL; > @@ -171,7 +171,7 @@ static struct ovl_fh *ovl_get_origin_fh(struct dentry *dentry) > goto out; > } > > -static struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt) > +struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt) > { > struct dentry *origin; > int bytes; > diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h > index f6fd999cb98e..c4f8e98e209e 100644 > --- a/fs/overlayfs/overlayfs.h > +++ b/fs/overlayfs/overlayfs.h > @@ -258,6 +258,8 @@ static inline bool ovl_is_impuredir(struct dentry *dentry) > > > /* namei.c */ > +int ovl_check_fh_len(struct ovl_fh *fh, int fh_len); > +struct dentry *ovl_decode_fh(struct ovl_fh *fh, struct vfsmount *mnt); > int ovl_verify_origin(struct dentry *dentry, struct dentry *origin, > bool is_upper, bool set); > int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index); > -- > 2.7.4 >