diff options
Diffstat (limited to 'fs/overlayfs')
| -rw-r--r-- | fs/overlayfs/copy_up.c | 82 | ||||
| -rw-r--r-- | fs/overlayfs/overlayfs.h | 36 |
2 files changed, 118 insertions, 0 deletions
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c index 906ea6c93260..9008ab9fbd2e 100644 --- a/fs/overlayfs/copy_up.c +++ b/fs/overlayfs/copy_up.c @@ -20,6 +20,7 @@ #include <linux/namei.h> #include <linux/fdtable.h> #include <linux/ratelimit.h> +#include <linux/exportfs.h> #include "overlayfs.h" #include "ovl_entry.h" @@ -232,6 +233,79 @@ int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat) return err; } +static struct ovl_fh *ovl_encode_fh(struct dentry *lower, uuid_be *uuid) +{ + struct ovl_fh *fh; + int fh_type, fh_len, dwords; + void *buf; + int buflen = MAX_HANDLE_SZ; + + buf = kmalloc(buflen, GFP_TEMPORARY); + if (!buf) + return ERR_PTR(-ENOMEM); + + /* + * We encode a non-connectable file handle for non-dir, because we + * only need to find the lower inode number and we don't want to pay + * the price or reconnecting the dentry. + */ + dwords = buflen >> 2; + fh_type = exportfs_encode_fh(lower, buf, &dwords, 0); + buflen = (dwords << 2); + + fh = ERR_PTR(-EIO); + if (WARN_ON(fh_type < 0) || + WARN_ON(buflen > MAX_HANDLE_SZ) || + WARN_ON(fh_type == FILEID_INVALID)) + goto out; + + BUILD_BUG_ON(MAX_HANDLE_SZ + offsetof(struct ovl_fh, fid) > 255); + fh_len = offsetof(struct ovl_fh, fid) + buflen; + fh = kmalloc(fh_len, GFP_KERNEL); + if (!fh) { + fh = ERR_PTR(-ENOMEM); + goto out; + } + + fh->version = OVL_FH_VERSION; + fh->magic = OVL_FH_MAGIC; + fh->type = fh_type; + fh->flags = OVL_FH_FLAG_CPU_ENDIAN; + fh->len = fh_len; + fh->uuid = *uuid; + memcpy(fh->fid, buf, buflen); + +out: + kfree(buf); + return fh; +} + +static int ovl_set_origin(struct dentry *dentry, struct dentry *lower, + struct dentry *upper) +{ + struct super_block *sb = lower->d_sb; + uuid_be *uuid = (uuid_be *) &sb->s_uuid; + const struct ovl_fh *fh = NULL; + int err; + + /* + * When lower layer doesn't support export operations store a 'null' fh, + * so we can use the overlay.origin xattr to distignuish between a copy + * up and a pure upper inode. + */ + if (sb->s_export_op && sb->s_export_op->fh_to_dentry && + uuid_be_cmp(*uuid, NULL_UUID_BE)) { + fh = ovl_encode_fh(lower, uuid); + if (IS_ERR(fh)) + return PTR_ERR(fh); + } + + err = ovl_do_setxattr(upper, OVL_XATTR_ORIGIN, fh, fh ? fh->len : 0, 0); + kfree(fh); + + return err; +} + static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir, struct dentry *dentry, struct path *lowerpath, struct kstat *stat, const char *link, @@ -316,6 +390,14 @@ static int ovl_copy_up_locked(struct dentry *workdir, struct dentry *upperdir, if (err) goto out_cleanup; + /* + * Store identifier of lower inode in upper inode xattr to + * allow lookup of the copy up origin inode. + */ + err = ovl_set_origin(dentry, lowerpath->dentry, temp); + if (err) + goto out_cleanup; + if (tmpfile) err = ovl_do_link(temp, udir, upper, true); else diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h index c851158324e2..77405e27cd64 100644 --- a/fs/overlayfs/overlayfs.h +++ b/fs/overlayfs/overlayfs.h @@ -8,6 +8,7 @@ */ #include <linux/kernel.h> +#include <linux/uuid.h> enum ovl_path_type { __OVL_PATH_UPPER = (1 << 0), @@ -20,6 +21,41 @@ enum ovl_path_type { #define OVL_XATTR_PREFIX XATTR_TRUSTED_PREFIX "overlay." #define OVL_XATTR_OPAQUE OVL_XATTR_PREFIX "opaque" #define OVL_XATTR_REDIRECT OVL_XATTR_PREFIX "redirect" +#define OVL_XATTR_ORIGIN OVL_XATTR_PREFIX "origin" + +/* + * The tuple (fh,uuid) is a universal unique identifier for a copy up origin, + * where: + * origin.fh - exported file handle of the lower file + * origin.uuid - uuid of the lower filesystem + */ +#define OVL_FH_VERSION 0 +#define OVL_FH_MAGIC 0xfb + +/* CPU byte order required for fid decoding: */ +#define OVL_FH_FLAG_BIG_ENDIAN (1 << 0) +#define OVL_FH_FLAG_ANY_ENDIAN (1 << 1) + +#define OVL_FH_FLAG_ALL (OVL_FH_FLAG_BIG_ENDIAN | OVL_FH_FLAG_ANY_ENDIAN) + +#if defined(__LITTLE_ENDIAN) +#define OVL_FH_FLAG_CPU_ENDIAN 0 +#elif defined(__BIG_ENDIAN) +#define OVL_FH_FLAG_CPU_ENDIAN OVL_FH_FLAG_BIG_ENDIAN +#else +#error Endianness not defined +#endif + +/* On-disk and in-memeory format for redirect by file handle */ +struct ovl_fh { + u8 version; /* 0 */ + u8 magic; /* 0xfb */ + u8 len; /* size of this header + size of fid */ + u8 flags; /* OVL_FH_FLAG_* */ + u8 type; /* fid_type of fid */ + uuid_be uuid; /* uuid of filesystem */ + u8 fid[0]; /* file identifier */ +} __packed; #define OVL_ISUPPER_MASK 1UL |