diff options
Diffstat (limited to 'fs/overlayfs/namei.c')
| -rw-r--r-- | fs/overlayfs/namei.c | 401 |
1 files changed, 401 insertions, 0 deletions
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c new file mode 100644 index 000000000000..9ad48d9202a9 --- /dev/null +++ b/fs/overlayfs/namei.c @@ -0,0 +1,401 @@ +/* + * Copyright (C) 2011 Novell Inc. + * Copyright (C) 2016 Red Hat, Inc. + * + * This program is free software; you can redistribute it and/or modify it + * under the terms of the GNU General Public License version 2 as published by + * the Free Software Foundation. + */ + +#include <linux/fs.h> +#include <linux/namei.h> +#include <linux/xattr.h> +#include <linux/ratelimit.h> +#include "overlayfs.h" +#include "ovl_entry.h" + +struct ovl_lookup_data { + struct qstr name; + bool is_dir; + bool opaque; + bool stop; + bool last; + char *redirect; +}; + +static int ovl_check_redirect(struct dentry *dentry, struct ovl_lookup_data *d, + size_t prelen, const char *post) +{ + int res; + char *s, *next, *buf = NULL; + + res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0); + if (res < 0) { + if (res == -ENODATA || res == -EOPNOTSUPP) + return 0; + goto fail; + } + buf = kzalloc(prelen + res + strlen(post) + 1, GFP_TEMPORARY); + if (!buf) + return -ENOMEM; + + if (res == 0) + goto invalid; + + res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res); + if (res < 0) + goto fail; + if (res == 0) + goto invalid; + if (buf[0] == '/') { + for (s = buf; *s++ == '/'; s = next) { + next = strchrnul(s, '/'); + if (s == next) + goto invalid; + } + } else { + if (strchr(buf, '/') != NULL) + goto invalid; + + 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; + +err_free: + kfree(buf); + return 0; +fail: + pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res); + goto err_free; +invalid: + pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf); + goto err_free; +} + +static bool ovl_is_opaquedir(struct dentry *dentry) +{ + int res; + char val; + + if (!d_is_dir(dentry)) + return false; + + res = vfs_getxattr(dentry, OVL_XATTR_OPAQUE, &val, 1); + if (res == 1 && val == 'y') + return true; + + return false; +} + +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) +{ + struct dentry *this; + int err; + + this = lookup_one_len_unlocked(name, base, namelen); + if (IS_ERR(this)) { + err = PTR_ERR(this); + this = NULL; + if (err == -ENOENT || err == -ENAMETOOLONG) + goto out; + goto out_err; + } + if (!this->d_inode) + goto put_and_out; + + 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; + } + if (!d_can_lookup(this)) { + d->stop = true; + if (d->is_dir) + goto put_and_out; + goto out; + } + d->is_dir = true; + if (!d->last && ovl_is_opaquedir(this)) { + d->stop = 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) +{ + const char *s = d->name.name; + struct dentry *dentry = NULL; + int err; + + if (*s != '/') + return ovl_lookup_single(base, d, d->name.name, d->name.len, + 0, "", ret); + + while (*s++ == '/' && !IS_ERR_OR_NULL(base) && d_can_lookup(base)) { + const char *next = strchrnul(s, '/'); + size_t slen = strlen(s); + + if (WARN_ON(slen > d->name.len) || + WARN_ON(strcmp(d->name.name + d->name.len - slen, s))) + return -EIO; + + err = ovl_lookup_single(base, d, s, next - s, + d->name.len - slen, next, &base); + dput(dentry); + if (err) + return err; + dentry = base; + s = next; + } + *ret = dentry; + return 0; +} + +/* + * 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 = oe->lowerstack[idx - 1]; + + return (idx < oe->numlower) ? idx + 1 : -1; +} + +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 path *stack = NULL; + struct dentry *upperdir, *upperdentry = NULL; + unsigned int ctr = 0; + struct inode *inode = NULL; + bool upperopaque = false; + char *upperredirect = NULL; + struct dentry *this; + unsigned int i; + int err; + struct ovl_lookup_data d = { + .name = dentry->d_name, + .is_dir = false, + .opaque = false, + .stop = false, + .last = !poe->numlower, + .redirect = NULL, + }; + + if (dentry->d_name.len > ofs->namelen) + return ERR_PTR(-ENAMETOOLONG); + + old_cred = ovl_override_creds(dentry->d_sb); + upperdir = ovl_upperdentry_dereference(poe); + if (upperdir) { + err = ovl_lookup_layer(upperdir, &d, &upperdentry); + if (err) + goto out; + + if (upperdentry && unlikely(ovl_dentry_remote(upperdentry))) { + dput(upperdentry); + err = -EREMOTE; + goto out; + } + + if (d.redirect) { + upperredirect = kstrdup(d.redirect, GFP_KERNEL); + if (!upperredirect) + goto out_put_upper; + if (d.redirect[0] == '/') + poe = dentry->d_sb->s_root->d_fsdata; + } + upperopaque = d.opaque; + } + + if (!d.stop && poe->numlower) { + err = -ENOMEM; + stack = kcalloc(ofs->numlower, sizeof(struct path), + GFP_TEMPORARY); + if (!stack) + goto out_put_upper; + } + + for (i = 0; !d.stop && i < poe->numlower; i++) { + struct path lowerpath = poe->lowerstack[i]; + + d.last = i == poe->numlower - 1; + err = ovl_lookup_layer(lowerpath.dentry, &d, &this); + if (err) + goto out_put; + + if (!this) + continue; + + stack[ctr].dentry = this; + stack[ctr].mnt = lowerpath.mnt; + ctr++; + + if (d.stop) + break; + + if (d.redirect && + d.redirect[0] == '/' && + poe != dentry->d_sb->s_root->d_fsdata) { + poe = dentry->d_sb->s_root->d_fsdata; + + /* Find the current layer on the root dentry */ + for (i = 0; i < poe->numlower; i++) + if (poe->lowerstack[i].mnt == lowerpath.mnt) + break; + if (WARN_ON(i == poe->numlower)) + break; + } + } + + oe = ovl_alloc_entry(ctr); + err = -ENOMEM; + if (!oe) + goto out_put; + + if (upperdentry || ctr) { + struct dentry *realdentry; + struct inode *realinode; + + realdentry = upperdentry ? upperdentry : stack[0].dentry; + realinode = d_inode(realdentry); + + err = -ENOMEM; + if (upperdentry && !d_is_dir(upperdentry)) { + inode = ovl_get_inode(dentry->d_sb, realinode); + } else { + inode = ovl_new_inode(dentry->d_sb, realinode->i_mode, + realinode->i_rdev); + if (inode) + ovl_inode_init(inode, realinode, !!upperdentry); + } + if (!inode) + goto out_free_oe; + ovl_copyattr(realdentry->d_inode, inode); + } + + revert_creds(old_cred); + oe->opaque = upperopaque; + oe->redirect = upperredirect; + oe->__upperdentry = upperdentry; + memcpy(oe->lowerstack, stack, sizeof(struct path) * ctr); + kfree(stack); + kfree(d.redirect); + dentry->d_fsdata = oe; + d_add(dentry, inode); + + return NULL; + +out_free_oe: + kfree(oe); +out_put: + for (i = 0; i < ctr; i++) + dput(stack[i].dentry); + kfree(stack); +out_put_upper: + 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 *oe = dentry->d_fsdata; + struct ovl_entry *poe = dentry->d_parent->d_fsdata; + const struct qstr *name = &dentry->d_name; + 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 oe->opaque; + + /* Negative upper -> positive lower */ + if (!oe->__upperdentry) + return true; + + /* 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_len_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 { + if (this->d_inode) { + positive = !ovl_is_whiteout(this); + done = true; + } + dput(this); + } + } + + return positive; +} |