diff options
| -rw-r--r-- | fs/overlayfs/namei.c | 132 |
1 files changed, 132 insertions, 0 deletions
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c index d0a3e4ad3042..bad0f665a635 100644 --- a/fs/overlayfs/namei.c +++ b/fs/overlayfs/namei.c @@ -12,6 +12,8 @@ #include <linux/namei.h> #include <linux/xattr.h> #include <linux/ratelimit.h> +#include <linux/mount.h> +#include <linux/exportfs.h> #include "overlayfs.h" #include "ovl_entry.h" @@ -81,6 +83,90 @@ invalid: goto err_free; } +static int ovl_acceptable(void *ctx, struct dentry *dentry) +{ + return 1; +} + +static struct dentry *ovl_get_origin(struct dentry *dentry, + struct vfsmount *mnt) +{ + int res; + struct ovl_fh *fh = NULL; + struct dentry *origin = NULL; + int bytes; + + res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, 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, GFP_TEMPORARY); + if (!fh) + return ERR_PTR(-ENOMEM); + + res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, fh, res); + if (res < 0) + goto fail; + + if (res < sizeof(struct ovl_fh) || res < fh->len) + goto invalid; + + if (fh->magic != OVL_FH_MAGIC) + goto invalid; + + /* Treat larger version and unknown flags as "origin unknown" */ + if (fh->version > OVL_FH_VERSION || fh->flags & ~OVL_FH_FLAG_ALL) + goto out; + + /* Treat endianness mismatch as "origin unknown" */ + if (!(fh->flags & OVL_FH_FLAG_ANY_ENDIAN) && + (fh->flags & OVL_FH_FLAG_BIG_ENDIAN) != OVL_FH_FLAG_CPU_ENDIAN) + goto out; + + bytes = (fh->len - offsetof(struct ovl_fh, fid)); + + /* + * Make sure that the stored uuid matches the uuid of the lower + * layer where file handle will be decoded. + */ + if (uuid_be_cmp(fh->uuid, *(uuid_be *) &mnt->mnt_sb->s_uuid)) + goto out; + + origin = exportfs_decode_fh(mnt, (struct fid *)fh->fid, + bytes >> 2, (int)fh->type, + ovl_acceptable, NULL); + if (IS_ERR(origin)) { + /* Treat stale file handle as "origin unknown" */ + if (origin == ERR_PTR(-ESTALE)) + origin = NULL; + goto out; + } + + if (ovl_dentry_weird(origin) || + ((d_inode(origin)->i_mode ^ d_inode(dentry)->i_mode) & S_IFMT)) { + dput(origin); + origin = NULL; + goto invalid; + } + +out: + kfree(fh); + return origin; + +fail: + pr_warn_ratelimited("overlayfs: failed to get origin (%i)\n", res); + goto out; +invalid: + pr_warn_ratelimited("overlayfs: invalid origin (%*phN)\n", res, fh); + goto out; +} + static bool ovl_is_opaquedir(struct dentry *dentry) { int res; @@ -192,6 +278,45 @@ static int ovl_lookup_layer(struct dentry *base, struct ovl_lookup_data *d, return 0; } + +static int ovl_check_origin(struct dentry *dentry, struct dentry *upperdentry, + struct path **stackp, unsigned int *ctrp) +{ + struct super_block *same_sb = ovl_same_sb(dentry->d_sb); + struct ovl_entry *roe = dentry->d_sb->s_root->d_fsdata; + struct vfsmount *mnt; + struct dentry *origin; + + if (!same_sb || !roe->numlower) + return 0; + + /* + * Since all layers are on the same fs, we use the first layer for + * decoding the 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 the first layer's 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 first layer that was moved under us. + */ + mnt = roe->lowerstack[0].mnt; + + origin = ovl_get_origin(upperdentry, mnt); + if (IS_ERR_OR_NULL(origin)) + return PTR_ERR(origin); + + BUG_ON(*stackp || *ctrp); + *stackp = kmalloc(sizeof(struct path), GFP_TEMPORARY); + if (!*stackp) { + dput(origin); + return -ENOMEM; + } + **stackp = (struct path) { .dentry = origin, .mnt = mnt }; + *ctrp = 1; + + return 0; +} + /* * Returns next layer in stack starting from top. * Returns -1 if this is the last layer. @@ -254,6 +379,13 @@ struct dentry *ovl_lookup(struct inode *dir, struct dentry *dentry, err = -EREMOTE; goto out; } + if (upperdentry && !d.is_dir) { + BUG_ON(!d.stop || d.redirect); + err = ovl_check_origin(dentry, upperdentry, + &stack, &ctr); + if (err) + goto out; + } if (d.redirect) { upperredirect = kstrdup(d.redirect, GFP_KERNEL); |