| // 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 qstr name; |
| bool is_dir; |
| bool opaque; |
| bool stop; |
| bool last; |
| char *redirect; |
| bool metacopy; |
| }; |
| |
| static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d, |
| size_t prelen, const char *post) |
| { |
| int res; |
| char *buf; |
| |
| buf = ovl_get_redirect_xattr(dentry, 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 decendant 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 dentry *dentry, const char *name) |
| { |
| int res, err; |
| struct ovl_fh *fh = NULL; |
| |
| res = vfs_getxattr(dentry, name, 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 = vfs_getxattr(dentry, name, 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_fh *fh, struct vfsmount *mnt, |
| bool connected) |
| { |
| struct dentry *real; |
| int bytes; |
| |
| /* |
| * Make sure that the stored uuid matches the uuid of the lower |
| * layer where file handle will be decoded. |
| */ |
| if (!uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_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 dentry *dentry) |
| { |
| return ovl_check_dir_xattr(dentry, OVL_XATTR_OPAQUE); |
| } |
| |
| static struct dentry *ovl_lookup_positive_unlocked(const char *name, |
| struct dentry *base, int len, |
| bool drop_negative) |
| { |
| struct dentry *ret = lookup_one_len_unlocked(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; |
| int err; |
| bool last_element = !post[0]; |
| |
| this = ovl_lookup_positive_unlocked(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; |
| } |
| if (!d_can_lookup(this)) { |
| if (d->is_dir || !last_element) { |
| d->stop = true; |
| goto put_and_out; |
| } |
| err = ovl_check_metacopy_xattr(this); |
| 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(this)) { |
| d->stop = true; |
| if (last_element) |
| d->opaque = true; |
| goto out; |
| } |
| } |
| err = ovl_check_redirect(this, 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(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) && |
| ((d_inode(origin)->i_mode ^ d_inode(upperdentry)->i_mode) & S_IFMT)) |
| 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 -EIO; |
| } |
| |
| static int ovl_check_origin(struct ovl_fs *ofs, struct dentry *upperdentry, |
| struct ovl_path **stackp, unsigned int *ctrp) |
| { |
| struct ovl_fh *fh = ovl_get_fh(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; |
| } |
| |
| if (WARN_ON(*ctrp)) |
| return -EIO; |
| |
| *ctrp = 1; |
| 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 dentry *dentry, const char *name, |
| const struct ovl_fh *fh) |
| { |
| struct ovl_fh *ofh = ovl_get_fh(dentry, name); |
| 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 dentry *dentry, const char *name, |
| struct dentry *real, bool is_upper, bool set) |
| { |
| struct inode *inode; |
| struct ovl_fh *fh; |
| int err; |
| |
| fh = ovl_encode_real_fh(real, is_upper); |
| err = PTR_ERR(fh); |
| if (IS_ERR(fh)) { |
| fh = NULL; |
| goto fail; |
| } |
| |
| err = ovl_verify_fh(dentry, name, fh); |
| if (set && err == -ENODATA) |
| err = ovl_do_setxattr(dentry, name, fh->buf, fh->fb.len, 0); |
| 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(index, OVL_XATTR_UPPER); |
| if (IS_ERR_OR_NULL(fh)) |
| return ERR_CAST(fh); |
| |
| upper = ovl_decode_real_fh(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(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(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 indentify |
| * the overlay inode. |
| */ |
| int ovl_get_index_name(struct dentry *origin, struct qstr *name) |
| { |
| struct ovl_fh *fh; |
| int err; |
| |
| fh = ovl_encode_real_fh(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(origin, &name); |
| if (err) |
| return ERR_PTR(err); |
| |
| index = lookup_positive_unlocked(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->i_mode ^ d_inode(origin)->i_mode) & S_IFMT)) { |
| /* |
| * 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(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 dentry *dentry, struct dentry *lower, |
| struct dentry *upper) |
| { |
| int err; |
| |
| if (ovl_check_origin_xattr(upper)) |
| return 0; |
| |
| err = ovl_want_write(dentry); |
| if (err) |
| return err; |
| |
| err = ovl_set_origin(dentry, 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) { |
| 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) { |
| unsigned int origin_ctr = 0; |
| |
| /* |
| * 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, |
| &origin_ctr); |
| 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; |
| |
| err = ovl_lookup_layer(lower.dentry, &d, &this, false); |
| if (err) |
| goto out_put; |
| |
| if (!this) |
| continue; |
| |
| if ((uppermetacopy || d.metacopy) && !ofs->config.metacopy) { |
| 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(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(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)) { |
| 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) { |
| upperdentry = dget(index); |
| upperredirect = ovl_get_redirect_xattr(upperdentry, 0); |
| if (IS_ERR(upperredirect)) { |
| err = PTR_ERR(upperredirect); |
| upperredirect = NULL; |
| goto out_free_oe; |
| } |
| } |
| |
| 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_update_reval(dentry, upperdentry, |
| DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE); |
| |
| 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_positive_unlocked(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; |
| } |