diff options
Diffstat (limited to 'fs/overlayfs/namei.c')
| -rw-r--r-- | fs/overlayfs/namei.c | 1203 |
1 files changed, 1203 insertions, 0 deletions
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c new file mode 100644 index 000000000..655d08d6f --- /dev/null +++ b/fs/overlayfs/namei.c @@ -0,0 +1,1203 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2011 Novell Inc. + * Copyright (C) 2016 Red Hat, Inc. + */ + +#include <linux/fs.h> +#include <linux/cred.h> +#include <linux/ctype.h> +#include <linux/namei.h> +#include <linux/xattr.h> +#include <linux/ratelimit.h> +#include <linux/mount.h> +#include <linux/exportfs.h> +#include "overlayfs.h" + +struct ovl_lookup_data { + struct super_block *sb; + struct vfsmount *mnt; + struct qstr name; + bool is_dir; + bool opaque; + bool stop; + bool last; + char *redirect; + bool metacopy; +}; + +static int ovl_check_redirect(const struct path *path, struct ovl_lookup_data *d, + size_t prelen, const char *post) +{ + int res; + char *buf; + struct ovl_fs *ofs = OVL_FS(d->sb); + + buf = ovl_get_redirect_xattr(ofs, path, prelen + strlen(post)); + if (IS_ERR_OR_NULL(buf)) + return PTR_ERR(buf); + + if (buf[0] == '/') { + /* + * One of the ancestor path elements in an absolute path + * lookup in ovl_lookup_layer() could have been opaque and + * that will stop further lookup in lower layers (d->stop=true) + * But we have found an absolute redirect in descendant path + * element and that should force continue lookup in lower + * layers (reset d->stop). + */ + d->stop = false; + } else { + res = strlen(buf) + 1; + memmove(buf + prelen, buf, res); + memcpy(buf, d->name.name, prelen); + } + + strcat(buf, post); + kfree(d->redirect); + d->redirect = buf; + d->name.name = d->redirect; + d->name.len = strlen(d->redirect); + + return 0; +} + +static int ovl_acceptable(void *ctx, struct dentry *dentry) +{ + /* + * A non-dir origin may be disconnected, which is fine, because + * we only need it for its unique inode number. + */ + if (!d_is_dir(dentry)) + return 1; + + /* Don't decode a deleted empty directory */ + if (d_unhashed(dentry)) + return 0; + + /* Check if directory belongs to the layer we are decoding from */ + return is_subdir(dentry, ((struct vfsmount *)ctx)->mnt_root); +} + +/* + * Check validity of an overlay file handle buffer. + * + * Return 0 for a valid file handle. + * Return -ENODATA for "origin unknown". + * Return <0 for an invalid file handle. + */ +int ovl_check_fb_len(struct ovl_fb *fb, int fb_len) +{ + if (fb_len < sizeof(struct ovl_fb) || fb_len < fb->len) + return -EINVAL; + + if (fb->magic != OVL_FH_MAGIC) + return -EINVAL; + + /* Treat larger version and unknown flags as "origin unknown" */ + if (fb->version > OVL_FH_VERSION || fb->flags & ~OVL_FH_FLAG_ALL) + return -ENODATA; + + /* Treat endianness mismatch as "origin unknown" */ + if (!(fb->flags & OVL_FH_FLAG_ANY_ENDIAN) && + (fb->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN) + return -ENODATA; + + return 0; +} + +static struct ovl_fh *ovl_get_fh(struct ovl_fs *ofs, struct dentry *upperdentry, + enum ovl_xattr ox) +{ + int res, err; + struct ovl_fh *fh = NULL; + + res = ovl_getxattr_upper(ofs, upperdentry, ox, NULL, 0); + if (res < 0) { + if (res == -ENODATA || res == -EOPNOTSUPP) + return NULL; + goto fail; + } + /* Zero size value means "copied up but origin unknown" */ + if (res == 0) + return NULL; + + fh = kzalloc(res + OVL_FH_WIRE_OFFSET, GFP_KERNEL); + if (!fh) + return ERR_PTR(-ENOMEM); + + res = ovl_getxattr_upper(ofs, upperdentry, ox, fh->buf, res); + if (res < 0) + goto fail; + + err = ovl_check_fb_len(&fh->fb, res); + if (err < 0) { + if (err == -ENODATA) + goto out; + goto invalid; + } + + return fh; + +out: + kfree(fh); + return NULL; + +fail: + pr_warn_ratelimited("failed to get origin (%i)\n", res); + goto out; +invalid: + pr_warn_ratelimited("invalid origin (%*phN)\n", res, fh); + goto out; +} + +struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh, + struct vfsmount *mnt, bool connected) +{ + struct dentry *real; + int bytes; + + if (!capable(CAP_DAC_READ_SEARCH)) + return NULL; + + /* + * Make sure that the stored uuid matches the uuid of the lower + * layer where file handle will be decoded. + * In case of uuid=off option just make sure that stored uuid is null. + */ + if (ofs->config.uuid ? !uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_uuid) : + !uuid_is_null(&fh->fb.uuid)) + return NULL; + + bytes = (fh->fb.len - offsetof(struct ovl_fb, fid)); + real = exportfs_decode_fh(mnt, (struct fid *)fh->fb.fid, + bytes >> 2, (int)fh->fb.type, + connected ? ovl_acceptable : NULL, mnt); + if (IS_ERR(real)) { + /* + * Treat stale file handle to lower file as "origin unknown". + * upper file handle could become stale when upper file is + * unlinked and this information is needed to handle stale + * index entries correctly. + */ + if (real == ERR_PTR(-ESTALE) && + !(fh->fb.flags & OVL_FH_FLAG_PATH_UPPER)) + real = NULL; + return real; + } + + if (ovl_dentry_weird(real)) { + dput(real); + return NULL; + } + + return real; +} + +static bool ovl_is_opaquedir(struct ovl_fs *ofs, const struct path *path) +{ + return ovl_path_check_dir_xattr(ofs, path, OVL_XATTR_OPAQUE); +} + +static struct dentry *ovl_lookup_positive_unlocked(struct ovl_lookup_data *d, + const char *name, + struct dentry *base, int len, + bool drop_negative) +{ + struct dentry *ret = lookup_one_unlocked(mnt_user_ns(d->mnt), name, base, len); + + if (!IS_ERR(ret) && d_flags_negative(smp_load_acquire(&ret->d_flags))) { + if (drop_negative && ret->d_lockref.count == 1) { + spin_lock(&ret->d_lock); + /* Recheck condition under lock */ + if (d_is_negative(ret) && ret->d_lockref.count == 1) + __d_drop(ret); + spin_unlock(&ret->d_lock); + } + dput(ret); + ret = ERR_PTR(-ENOENT); + } + return ret; +} + +static int ovl_lookup_single(struct dentry *base, struct ovl_lookup_data *d, + const char *name, unsigned int namelen, + size_t prelen, const char *post, + struct dentry **ret, bool drop_negative) +{ + struct dentry *this; + struct path path; + int err; + bool last_element = !post[0]; + + this = ovl_lookup_positive_unlocked(d, name, base, namelen, drop_negative); + if (IS_ERR(this)) { + err = PTR_ERR(this); + this = NULL; + if (err == -ENOENT || err == -ENAMETOOLONG) + goto out; + goto out_err; + } + + if (ovl_dentry_weird(this)) { + /* Don't support traversing automounts and other weirdness */ + err = -EREMOTE; + goto out_err; + } + if (ovl_is_whiteout(this)) { + d->stop = d->opaque = true; + goto put_and_out; + } + /* + * This dentry should be a regular file if previous layer lookup + * found a metacopy dentry. + */ + if (last_element && d->metacopy && !d_is_reg(this)) { + d->stop = true; + goto put_and_out; + } + + path.dentry = this; + path.mnt = d->mnt; + if (!d_can_lookup(this)) { + if (d->is_dir || !last_element) { + d->stop = true; + goto put_and_out; + } + err = ovl_check_metacopy_xattr(OVL_FS(d->sb), &path); + if (err < 0) + goto out_err; + + d->metacopy = err; + d->stop = !d->metacopy; + if (!d->metacopy || d->last) + goto out; + } else { + if (ovl_lookup_trap_inode(d->sb, this)) { + /* Caught in a trap of overlapping layers */ + err = -ELOOP; + goto out_err; + } + + if (last_element) + d->is_dir = true; + if (d->last) + goto out; + + if (ovl_is_opaquedir(OVL_FS(d->sb), &path)) { + d->stop = true; + if (last_element) + d->opaque = true; + goto out; + } + } + err = ovl_check_redirect(&path, d, prelen, post); + if (err) + goto out_err; +out: + *ret = this; + return 0; + +put_and_out: + dput(this); + this = NULL; + goto out; + +out_err: + dput(this); + return err; +} + +static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d, + struct dentry **ret, bool drop_negative) +{ + /* Counting down from the end, since the prefix can change */ + size_t rem = d->name.len - 1; + struct dentry *dentry = NULL; + int err; + + if (d->name.name[0] != '/') + return ovl_lookup_single(base, d, d->name.name, d->name.len, + 0, "", ret, drop_negative); + + while (!IS_ERR_OR_NULL(base) && d_can_lookup(base)) { + const char *s = d->name.name + d->name.len - rem; + const char *next = strchrnul(s, '/'); + size_t thislen = next - s; + bool end = !next[0]; + + /* Verify we did not go off the rails */ + if (WARN_ON(s[-1] != '/')) + return -EIO; + + err = ovl_lookup_single(base, d, s, thislen, + d->name.len - rem, next, &base, + drop_negative); + dput(dentry); + if (err) + return err; + dentry = base; + if (end) + break; + + rem -= thislen + 1; + + if (WARN_ON(rem >= d->name.len)) + return -EIO; + } + *ret = dentry; + return 0; +} + + +int ovl_check_origin_fh(struct ovl_fs *ofs, struct ovl_fh *fh, bool connected, + struct dentry *upperdentry, struct ovl_path **stackp) +{ + struct dentry *origin = NULL; + int i; + + for (i = 1; i < ofs->numlayer; i++) { + /* + * If lower fs uuid is not unique among lower fs we cannot match + * fh->uuid to layer. + */ + if (ofs->layers[i].fsid && + ofs->layers[i].fs->bad_uuid) + continue; + + origin = ovl_decode_real_fh(ofs, fh, ofs->layers[i].mnt, + connected); + if (origin) + break; + } + + if (!origin) + return -ESTALE; + else if (IS_ERR(origin)) + return PTR_ERR(origin); + + if (upperdentry && !ovl_is_whiteout(upperdentry) && + inode_wrong_type(d_inode(upperdentry), d_inode(origin)->i_mode)) + goto invalid; + + if (!*stackp) + *stackp = kmalloc(sizeof(struct ovl_path), GFP_KERNEL); + if (!*stackp) { + dput(origin); + return -ENOMEM; + } + **stackp = (struct ovl_path){ + .dentry = origin, + .layer = &ofs->layers[i] + }; + + return 0; + +invalid: + pr_warn_ratelimited("invalid origin (%pd2, ftype=%x, origin ftype=%x).\n", + upperdentry, d_inode(upperdentry)->i_mode & S_IFMT, + d_inode(origin)->i_mode & S_IFMT); + dput(origin); + return -ESTALE; +} + +static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry, + struct ovl_path **stackp) +{ + struct ovl_fh *fh = ovl_get_fh(ofs, upperdentry, OVL_XATTR_ORIGIN); + int err; + + if (IS_ERR_OR_NULL(fh)) + return PTR_ERR(fh); + + err = ovl_check_origin_fh(ofs, fh, false, upperdentry, stackp); + kfree(fh); + + if (err) { + if (err == -ESTALE) + return 0; + return err; + } + + return 0; +} + +/* + * Verify that @fh matches the file handle stored in xattr @name. + * Return 0 on match, -ESTALE on mismatch, < 0 on error. + */ +static int ovl_verify_fh(struct ovl_fs *ofs, struct dentry *dentry, + enum ovl_xattr ox, const struct ovl_fh *fh) +{ + struct ovl_fh *ofh = ovl_get_fh(ofs, dentry, ox); + int err = 0; + + if (!ofh) + return -ENODATA; + + if (IS_ERR(ofh)) + return PTR_ERR(ofh); + + if (fh->fb.len != ofh->fb.len || memcmp(&fh->fb, &ofh->fb, fh->fb.len)) + err = -ESTALE; + + kfree(ofh); + return err; +} + +/* + * Verify that @real dentry matches the file handle stored in xattr @name. + * + * If @set is true and there is no stored file handle, encode @real and store + * file handle in xattr @name. + * + * Return 0 on match, -ESTALE on mismatch, -ENODATA on no xattr, < 0 on error. + */ +int ovl_verify_set_fh(struct ovl_fs *ofs, struct dentry *dentry, + enum ovl_xattr ox, struct dentry *real, bool is_upper, + bool set) +{ + struct inode *inode; + struct ovl_fh *fh; + int err; + + fh = ovl_encode_real_fh(ofs, real, is_upper); + err = PTR_ERR(fh); + if (IS_ERR(fh)) { + fh = NULL; + goto fail; + } + + err = ovl_verify_fh(ofs, dentry, ox, fh); + if (set && err == -ENODATA) + err = ovl_setxattr(ofs, dentry, ox, fh->buf, fh->fb.len); + if (err) + goto fail; + +out: + kfree(fh); + return err; + +fail: + inode = d_inode(real); + pr_warn_ratelimited("failed to verify %s (%pd2, ino=%lu, err=%i)\n", + is_upper ? "upper" : "origin", real, + inode ? inode->i_ino : 0, err); + goto out; +} + +/* Get upper dentry from index */ +struct dentry *ovl_index_upper(struct ovl_fs *ofs, struct dentry *index) +{ + struct ovl_fh *fh; + struct dentry *upper; + + if (!d_is_dir(index)) + return dget(index); + + fh = ovl_get_fh(ofs, index, OVL_XATTR_UPPER); + if (IS_ERR_OR_NULL(fh)) + return ERR_CAST(fh); + + upper = ovl_decode_real_fh(ofs, fh, ovl_upper_mnt(ofs), true); + kfree(fh); + + if (IS_ERR_OR_NULL(upper)) + return upper ?: ERR_PTR(-ESTALE); + + if (!d_is_dir(upper)) { + pr_warn_ratelimited("invalid index upper (%pd2, upper=%pd2).\n", + index, upper); + dput(upper); + return ERR_PTR(-EIO); + } + + return upper; +} + +/* + * Verify that an index entry name matches the origin file handle stored in + * OVL_XATTR_ORIGIN and that origin file handle can be decoded to lower path. + * Return 0 on match, -ESTALE on mismatch or stale origin, < 0 on error. + */ +int ovl_verify_index(struct ovl_fs *ofs, struct dentry *index) +{ + struct ovl_fh *fh = NULL; + size_t len; + struct ovl_path origin = { }; + struct ovl_path *stack = &origin; + struct dentry *upper = NULL; + int err; + + if (!d_inode(index)) + return 0; + + err = -EINVAL; + if (index->d_name.len < sizeof(struct ovl_fb)*2) + goto fail; + + err = -ENOMEM; + len = index->d_name.len / 2; + fh = kzalloc(len + OVL_FH_WIRE_OFFSET, GFP_KERNEL); + if (!fh) + goto fail; + + err = -EINVAL; + if (hex2bin(fh->buf, index->d_name.name, len)) + goto fail; + + err = ovl_check_fb_len(&fh->fb, len); + if (err) + goto fail; + + /* + * Whiteout index entries are used as an indication that an exported + * overlay file handle should be treated as stale (i.e. after unlink + * of the overlay inode). These entries contain no origin xattr. + */ + if (ovl_is_whiteout(index)) + goto out; + + /* + * Verifying directory index entries are not stale is expensive, so + * only verify stale dir index if NFS export is enabled. + */ + if (d_is_dir(index) && !ofs->config.nfs_export) + goto out; + + /* + * Directory index entries should have 'upper' xattr pointing to the + * real upper dir. Non-dir index entries are hardlinks to the upper + * real inode. For non-dir index, we can read the copy up origin xattr + * directly from the index dentry, but for dir index we first need to + * decode the upper directory. + */ + upper = ovl_index_upper(ofs, index); + if (IS_ERR_OR_NULL(upper)) { + err = PTR_ERR(upper); + /* + * Directory index entries with no 'upper' xattr need to be + * removed. When dir index entry has a stale 'upper' xattr, + * we assume that upper dir was removed and we treat the dir + * index as orphan entry that needs to be whited out. + */ + if (err == -ESTALE) + goto orphan; + else if (!err) + err = -ESTALE; + goto fail; + } + + err = ovl_verify_fh(ofs, upper, OVL_XATTR_ORIGIN, fh); + dput(upper); + if (err) + goto fail; + + /* Check if non-dir index is orphan and don't warn before cleaning it */ + if (!d_is_dir(index) && d_inode(index)->i_nlink == 1) { + err = ovl_check_origin_fh(ofs, fh, false, index, &stack); + if (err) + goto fail; + + if (ovl_get_nlink(ofs, origin.dentry, index, 0) == 0) + goto orphan; + } + +out: + dput(origin.dentry); + kfree(fh); + return err; + +fail: + pr_warn_ratelimited("failed to verify index (%pd2, ftype=%x, err=%i)\n", + index, d_inode(index)->i_mode & S_IFMT, err); + goto out; + +orphan: + pr_warn_ratelimited("orphan index entry (%pd2, ftype=%x, nlink=%u)\n", + index, d_inode(index)->i_mode & S_IFMT, + d_inode(index)->i_nlink); + err = -ENOENT; + goto out; +} + +static int ovl_get_index_name_fh(struct ovl_fh *fh, struct qstr *name) +{ + char *n, *s; + + n = kcalloc(fh->fb.len, 2, GFP_KERNEL); + if (!n) + return -ENOMEM; + + s = bin2hex(n, fh->buf, fh->fb.len); + *name = (struct qstr) QSTR_INIT(n, s - n); + + return 0; + +} + +/* + * Lookup in indexdir for the index entry of a lower real inode or a copy up + * origin inode. The index entry name is the hex representation of the lower + * inode file handle. + * + * If the index dentry in negative, then either no lower aliases have been + * copied up yet, or aliases have been copied up in older kernels and are + * not indexed. + * + * If the index dentry for a copy up origin inode is positive, but points + * to an inode different than the upper inode, then either the upper inode + * has been copied up and not indexed or it was indexed, but since then + * index dir was cleared. Either way, that index cannot be used to identify + * the overlay inode. + */ +int ovl_get_index_name(struct ovl_fs *ofs, struct dentry *origin, + struct qstr *name) +{ + struct ovl_fh *fh; + int err; + + fh = ovl_encode_real_fh(ofs, origin, false); + if (IS_ERR(fh)) + return PTR_ERR(fh); + + err = ovl_get_index_name_fh(fh, name); + + kfree(fh); + return err; +} + +/* Lookup index by file handle for NFS export */ +struct dentry *ovl_get_index_fh(struct ovl_fs *ofs, struct ovl_fh *fh) +{ + struct dentry *index; + struct qstr name; + int err; + + err = ovl_get_index_name_fh(fh, &name); + if (err) + return ERR_PTR(err); + + index = lookup_positive_unlocked(name.name, ofs->indexdir, name.len); + kfree(name.name); + if (IS_ERR(index)) { + if (PTR_ERR(index) == -ENOENT) + index = NULL; + return index; + } + + if (ovl_is_whiteout(index)) + err = -ESTALE; + else if (ovl_dentry_weird(index)) + err = -EIO; + else + return index; + + dput(index); + return ERR_PTR(err); +} + +struct dentry *ovl_lookup_index(struct ovl_fs *ofs, struct dentry *upper, + struct dentry *origin, bool verify) +{ + struct dentry *index; + struct inode *inode; + struct qstr name; + bool is_dir = d_is_dir(origin); + int err; + + err = ovl_get_index_name(ofs, origin, &name); + if (err) + return ERR_PTR(err); + + index = lookup_one_positive_unlocked(ovl_upper_mnt_userns(ofs), name.name, + ofs->indexdir, name.len); + if (IS_ERR(index)) { + err = PTR_ERR(index); + if (err == -ENOENT) { + index = NULL; + goto out; + } + pr_warn_ratelimited("failed inode index lookup (ino=%lu, key=%.*s, err=%i);\n" + "overlayfs: mount with '-o index=off' to disable inodes index.\n", + d_inode(origin)->i_ino, name.len, name.name, + err); + goto out; + } + + inode = d_inode(index); + if (ovl_is_whiteout(index) && !verify) { + /* + * When index lookup is called with !verify for decoding an + * overlay file handle, a whiteout index implies that decode + * should treat file handle as stale and no need to print a + * warning about it. + */ + dput(index); + index = ERR_PTR(-ESTALE); + goto out; + } else if (ovl_dentry_weird(index) || ovl_is_whiteout(index) || + inode_wrong_type(inode, d_inode(origin)->i_mode)) { + /* + * Index should always be of the same file type as origin + * except for the case of a whiteout index. A whiteout + * index should only exist if all lower aliases have been + * unlinked, which means that finding a lower origin on lookup + * whose index is a whiteout should be treated as an error. + */ + pr_warn_ratelimited("bad index found (index=%pd2, ftype=%x, origin ftype=%x).\n", + index, d_inode(index)->i_mode & S_IFMT, + d_inode(origin)->i_mode & S_IFMT); + goto fail; + } else if (is_dir && verify) { + if (!upper) { + pr_warn_ratelimited("suspected uncovered redirected dir found (origin=%pd2, index=%pd2).\n", + origin, index); + goto fail; + } + + /* Verify that dir index 'upper' xattr points to upper dir */ + err = ovl_verify_upper(ofs, index, upper, false); + if (err) { + if (err == -ESTALE) { + pr_warn_ratelimited("suspected multiply redirected dir found (upper=%pd2, origin=%pd2, index=%pd2).\n", + upper, origin, index); + } + goto fail; + } + } else if (upper && d_inode(upper) != inode) { + goto out_dput; + } +out: + kfree(name.name); + return index; + +out_dput: + dput(index); + index = NULL; + goto out; + +fail: + dput(index); + index = ERR_PTR(-EIO); + goto out; +} + +/* + * Returns next layer in stack starting from top. + * Returns -1 if this is the last layer. + */ +int ovl_path_next(int idx, struct dentry *dentry, struct path *path) +{ + struct ovl_entry *oe = dentry->d_fsdata; + + BUG_ON(idx < 0); + if (idx == 0) { + ovl_path_upper(dentry, path); + if (path->dentry) + return oe->numlower ? 1 : -1; + idx++; + } + BUG_ON(idx > oe->numlower); + path->dentry = oe->lowerstack[idx - 1].dentry; + path->mnt = oe->lowerstack[idx - 1].layer->mnt; + + return (idx < oe->numlower) ? idx + 1 : -1; +} + +/* Fix missing 'origin' xattr */ +static int ovl_fix_origin(struct ovl_fs *ofs, struct dentry *dentry, + struct dentry *lower, struct dentry *upper) +{ + int err; + + if (ovl_check_origin_xattr(ofs, upper)) + return 0; + + err = ovl_want_write(dentry); + if (err) + return err; + + err = ovl_set_origin(ofs, lower, upper); + if (!err) + err = ovl_set_impure(dentry->d_parent, upper->d_parent); + + ovl_drop_write(dentry); + return err; +} + +struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, + unsigned int flags) +{ + struct ovl_entry *oe; + const struct cred *old_cred; + struct ovl_fs *ofs = dentry->d_sb->s_fs_info; + struct ovl_entry *poe = dentry->d_parent->d_fsdata; + struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata; + struct ovl_path *stack = NULL, *origin_path = NULL; + struct dentry *upperdir, *upperdentry = NULL; + struct dentry *origin = NULL; + struct dentry *index = NULL; + unsigned int ctr = 0; + struct inode *inode = NULL; + bool upperopaque = false; + char *upperredirect = NULL; + struct dentry *this; + unsigned int i; + int err; + bool uppermetacopy = false; + struct ovl_lookup_data d = { + .sb = dentry->d_sb, + .name = dentry->d_name, + .is_dir = false, + .opaque = false, + .stop = false, + .last = ofs->config.redirect_follow ? false : !poe->numlower, + .redirect = NULL, + .metacopy = false, + }; + + if (dentry->d_name.len > ofs->namelen) + return ERR_PTR(-ENAMETOOLONG); + + old_cred = ovl_override_creds(dentry->d_sb); + upperdir = ovl_dentry_upper(dentry->d_parent); + if (upperdir) { + d.mnt = ovl_upper_mnt(ofs); + err = ovl_lookup_layer(upperdir, &d, &upperdentry, true); + if (err) + goto out; + + if (upperdentry && upperdentry->d_flags & DCACHE_OP_REAL) { + dput(upperdentry); + err = -EREMOTE; + goto out; + } + if (upperdentry && !d.is_dir) { + /* + * Lookup copy up origin by decoding origin file handle. + * We may get a disconnected dentry, which is fine, + * because we only need to hold the origin inode in + * cache and use its inode number. We may even get a + * connected dentry, that is not under any of the lower + * layers root. That is also fine for using it's inode + * number - it's the same as if we held a reference + * to a dentry in lower layer that was moved under us. + */ + err = ovl_check_origin(ofs, upperdentry, &origin_path); + if (err) + goto out_put_upper; + + if (d.metacopy) + uppermetacopy = true; + } + + if (d.redirect) { + err = -ENOMEM; + upperredirect = kstrdup(d.redirect, GFP_KERNEL); + if (!upperredirect) + goto out_put_upper; + if (d.redirect[0] == '/') + poe = roe; + } + upperopaque = d.opaque; + } + + if (!d.stop && poe->numlower) { + err = -ENOMEM; + stack = kcalloc(ofs->numlayer - 1, sizeof(struct ovl_path), + GFP_KERNEL); + if (!stack) + goto out_put_upper; + } + + for (i = 0; !d.stop && i < poe->numlower; i++) { + struct ovl_path lower = poe->lowerstack[i]; + + if (!ofs->config.redirect_follow) + d.last = i == poe->numlower - 1; + else + d.last = lower.layer->idx == roe->numlower; + + d.mnt = lower.layer->mnt; + err = ovl_lookup_layer(lower.dentry, &d, &this, false); + if (err) + goto out_put; + + if (!this) + continue; + + if ((uppermetacopy || d.metacopy) && !ofs->config.metacopy) { + dput(this); + err = -EPERM; + pr_warn_ratelimited("refusing to follow metacopy origin for (%pd2)\n", dentry); + goto out_put; + } + + /* + * If no origin fh is stored in upper of a merge dir, store fh + * of lower dir and set upper parent "impure". + */ + if (upperdentry && !ctr && !ofs->noxattr && d.is_dir) { + err = ovl_fix_origin(ofs, dentry, this, upperdentry); + if (err) { + dput(this); + goto out_put; + } + } + + /* + * When "verify_lower" feature is enabled, do not merge with a + * lower dir that does not match a stored origin xattr. In any + * case, only verified origin is used for index lookup. + * + * For non-dir dentry, if index=on, then ensure origin + * matches the dentry found using path based lookup, + * otherwise error out. + */ + if (upperdentry && !ctr && + ((d.is_dir && ovl_verify_lower(dentry->d_sb)) || + (!d.is_dir && ofs->config.index && origin_path))) { + err = ovl_verify_origin(ofs, upperdentry, this, false); + if (err) { + dput(this); + if (d.is_dir) + break; + goto out_put; + } + origin = this; + } + + if (d.metacopy && ctr) { + /* + * Do not store intermediate metacopy dentries in + * lower chain, except top most lower metacopy dentry. + * Continue the loop so that if there is an absolute + * redirect on this dentry, poe can be reset to roe. + */ + dput(this); + this = NULL; + } else { + stack[ctr].dentry = this; + stack[ctr].layer = lower.layer; + ctr++; + } + + /* + * Following redirects can have security consequences: it's like + * a symlink into the lower layer without the permission checks. + * This is only a problem if the upper layer is untrusted (e.g + * comes from an USB drive). This can allow a non-readable file + * or directory to become readable. + * + * Only following redirects when redirects are enabled disables + * this attack vector when not necessary. + */ + err = -EPERM; + if (d.redirect && !ofs->config.redirect_follow) { + pr_warn_ratelimited("refusing to follow redirect for (%pd2)\n", + dentry); + goto out_put; + } + + if (d.stop) + break; + + if (d.redirect && d.redirect[0] == '/' && poe != roe) { + poe = roe; + /* Find the current layer on the root dentry */ + i = lower.layer->idx - 1; + } + } + + /* + * For regular non-metacopy upper dentries, there is no lower + * path based lookup, hence ctr will be zero. If a dentry is found + * using ORIGIN xattr on upper, install it in stack. + * + * For metacopy dentry, path based lookup will find lower dentries. + * Just make sure a corresponding data dentry has been found. + */ + if (d.metacopy || (uppermetacopy && !ctr)) { + pr_warn_ratelimited("metacopy with no lower data found - abort lookup (%pd2)\n", + dentry); + err = -EIO; + goto out_put; + } else if (!d.is_dir && upperdentry && !ctr && origin_path) { + if (WARN_ON(stack != NULL)) { + err = -EIO; + goto out_put; + } + stack = origin_path; + ctr = 1; + origin = origin_path->dentry; + origin_path = NULL; + } + + /* + * Always lookup index if there is no-upperdentry. + * + * For the case of upperdentry, we have set origin by now if it + * needed to be set. There are basically three cases. + * + * For directories, lookup index by lower inode and verify it matches + * upper inode. We only trust dir index if we verified that lower dir + * matches origin, otherwise dir index entries may be inconsistent + * and we ignore them. + * + * For regular upper, we already set origin if upper had ORIGIN + * xattr. There is no verification though as there is no path + * based dentry lookup in lower in this case. + * + * For metacopy upper, we set a verified origin already if index + * is enabled and if upper had an ORIGIN xattr. + * + */ + if (!upperdentry && ctr) + origin = stack[0].dentry; + + if (origin && ovl_indexdir(dentry->d_sb) && + (!d.is_dir || ovl_index_all(dentry->d_sb))) { + index = ovl_lookup_index(ofs, upperdentry, origin, true); + if (IS_ERR(index)) { + err = PTR_ERR(index); + index = NULL; + goto out_put; + } + } + + oe = ovl_alloc_entry(ctr); + err = -ENOMEM; + if (!oe) + goto out_put; + + memcpy(oe->lowerstack, stack, sizeof(struct ovl_path) * ctr); + dentry->d_fsdata = oe; + + if (upperopaque) + ovl_dentry_set_opaque(dentry); + + if (upperdentry) + ovl_dentry_set_upper_alias(dentry); + else if (index) { + struct path upperpath = { + .dentry = upperdentry = dget(index), + .mnt = ovl_upper_mnt(ofs), + }; + + upperredirect = ovl_get_redirect_xattr(ofs, &upperpath, 0); + if (IS_ERR(upperredirect)) { + err = PTR_ERR(upperredirect); + upperredirect = NULL; + goto out_free_oe; + } + err = ovl_check_metacopy_xattr(ofs, &upperpath); + if (err < 0) + goto out_free_oe; + uppermetacopy = err; + } + + if (upperdentry || ctr) { + struct ovl_inode_params oip = { + .upperdentry = upperdentry, + .lowerpath = stack, + .index = index, + .numlower = ctr, + .redirect = upperredirect, + .lowerdata = (ctr > 1 && !d.is_dir) ? + stack[ctr - 1].dentry : NULL, + }; + + inode = ovl_get_inode(dentry->d_sb, &oip); + err = PTR_ERR(inode); + if (IS_ERR(inode)) + goto out_free_oe; + if (upperdentry && !uppermetacopy) + ovl_set_flag(OVL_UPPERDATA, inode); + } + + ovl_dentry_init_reval(dentry, upperdentry); + + revert_creds(old_cred); + if (origin_path) { + dput(origin_path->dentry); + kfree(origin_path); + } + dput(index); + kfree(stack); + kfree(d.redirect); + return d_splice_alias(inode, dentry); + +out_free_oe: + dentry->d_fsdata = NULL; + kfree(oe); +out_put: + dput(index); + for (i = 0; i < ctr; i++) + dput(stack[i].dentry); + kfree(stack); +out_put_upper: + if (origin_path) { + dput(origin_path->dentry); + kfree(origin_path); + } + dput(upperdentry); + kfree(upperredirect); +out: + kfree(d.redirect); + revert_creds(old_cred); + return ERR_PTR(err); +} + +bool ovl_lower_positive(struct dentry *dentry) +{ + struct ovl_entry *poe = dentry->d_parent->d_fsdata; + const struct qstr *name = &dentry->d_name; + const struct cred *old_cred; + unsigned int i; + bool positive = false; + bool done = false; + + /* + * If dentry is negative, then lower is positive iff this is a + * whiteout. + */ + if (!dentry->d_inode) + return ovl_dentry_is_opaque(dentry); + + /* Negative upper -> positive lower */ + if (!ovl_dentry_upper(dentry)) + return true; + + old_cred = ovl_override_creds(dentry->d_sb); + /* Positive upper -> have to look up lower to see whether it exists */ + for (i = 0; !done && !positive && i < poe->numlower; i++) { + struct dentry *this; + struct dentry *lowerdir = poe->lowerstack[i].dentry; + + this = lookup_one_positive_unlocked(mnt_user_ns(poe->lowerstack[i].layer->mnt), + name->name, lowerdir, name->len); + if (IS_ERR(this)) { + switch (PTR_ERR(this)) { + case -ENOENT: + case -ENAMETOOLONG: + break; + + default: + /* + * Assume something is there, we just couldn't + * access it. + */ + positive = true; + break; + } + } else { + positive = !ovl_is_whiteout(this); + done = true; + dput(this); + } + } + revert_creds(old_cred); + + return positive; +} |