cregit-Linux how code gets into the kernel

Release 4.10 fs/overlayfs/namei.c

Directory: fs/overlayfs
/*
 * 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; }

Contributors

PersonTokensPropCommitsCommitProp
miklos szeredimiklos szeredi313100.00%1100.00%
Total313100.00%1100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
miklos szeredimiklos szeredi58100.00%2100.00%
Total58100.00%2100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
miklos szeredimiklos szeredi261100.00%4100.00%
Total261100.00%4100.00%


static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d, struct dentry **ret) { /* 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); 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); 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; }

Contributors

PersonTokensPropCommitsCommitProp
miklos szeredimiklos szeredi16066.39%375.00%
amir goldsteinamir goldstein8133.61%125.00%
Total241100.00%4100.00%

/* * 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; }

Contributors

PersonTokensPropCommitsCommitProp
miklos szeredimiklos szeredi105100.00%1100.00%
Total105100.00%1100.00%


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); }

Contributors

PersonTokensPropCommitsCommitProp
miklos szeredimiklos szeredi792100.00%4100.00%
Total792100.00%4100.00%


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; }

Contributors

PersonTokensPropCommitsCommitProp
miklos szeredimiklos szeredi202100.00%1100.00%
Total202100.00%1100.00%


Overall Contributors

PersonTokensPropCommitsCommitProp
miklos szeredimiklos szeredi193695.98%480.00%
amir goldsteinamir goldstein814.02%120.00%
Total2017100.00%5100.00%
Directory: fs/overlayfs
Information contained on this website is for historical information purposes only and does not indicate or represent copyright ownership.