Commit b7bf9908 authored by Amir Goldstein's avatar Amir Goldstein Committed by Miklos Szeredi
Browse files

ovl: fix corner case of non-constant st_dev;st_ino 



On non-samefs overlay without xino, non pure upper inodes should use a
pseudo_dev assigned to each unique lower fs, but if lower layer is on the
same fs and upper layer, it has no pseudo_dev assigned.

In this overlay layers setup:
 - two filesystems, A and B
 - upper layer is on A
 - lower layer 1 is also on A
 - lower layer 2 is on B

Non pure upper overlay inode, whose origin is in layer 1 will have the
st_dev;st_ino values of the real lower inode before copy up and the
st_dev;st_ino values of the real upper inode after copy up.

Fix this inconsitency by assigning a unique pseudo_dev also for upper fs,
that will be used as st_dev value along with the lower inode st_dev for
overlay inodes in the case above.

Signed-off-by: default avatarAmir Goldstein <amir73il@gmail.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@redhat.com>
parent 1b81dddd

fs/overlayfs/inode.c

+4 −12
Original line number Diff line number Diff line
@@ -121,13 +121,12 @@ static int ovl_map_dev_ino(struct dentry *dentry, struct kstat *stat, int fsid) 
		 */

		stat->dev = dentry->d_sb->s_dev;

		stat->ino = dentry->d_inode->i_ino;

	} else if (fsid) {

	} else {

		/*

		 * For non-samefs setup, if we cannot map all layers st_ino

		 * to a unified address space, we need to make sure that st_dev

		 * is unique per lower fs. Upper layer uses real st_dev and

		 * lower layers use the unique anonymous bdev assigned to the

		 * lower fs.

		 * is unique per underlying fs, so we use the unique anonymous

		 * bdev assigned to the underlying fs.

		 */

		stat->dev = OVL_FS(dentry->d_sb)->fs[fsid].pseudo_dev;

	}
@@ -143,7 +142,6 @@ int ovl_getattr(const struct path *path, struct kstat *stat, 
	struct path realpath;

	const struct cred *old_cred;

	bool is_dir = S_ISDIR(dentry->d_inode->i_mode);

	bool samefs = ovl_same_fs(dentry->d_sb);

	int fsid = 0;

	int err;

	bool metacopy_blocks = false;
@@ -198,12 +196,6 @@ int ovl_getattr(const struct path *path, struct kstat *stat, 
			    (!ovl_verify_lower(dentry->d_sb) &&

			     (is_dir || lowerstat.nlink == 1))) {

				fsid = ovl_layer_lower(dentry)->fsid;

				/*

				 * Cannot use origin st_dev;st_ino because

				 * origin inode content may differ from overlay

				 * inode content.

				 */

				if (samefs || fsid)

				stat->ino = lowerstat.ino;

			}

fs/overlayfs/super.c

+10 −5
Original line number Diff line number Diff line
@@ -229,8 +229,7 @@ static void ovl_free_fs(struct ovl_fs *ofs) 
		mntput(ofs->layers[i].mnt);

	}

	kfree(ofs->layers);

	/* fs[0].pseudo_dev is either null or real upper st_dev */

	for (i = 1; i < ofs->numfs; i++)

	for (i = 0; i < ofs->numfs; i++)

		free_anon_bdev(ofs->fs[i].pseudo_dev);

	kfree(ofs->fs);
@@ -1341,13 +1340,19 @@ static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs, 
	ofs->numlayer = 1;



	/*

	 * All lower layers that share the same fs as upper layer, use the real

	 * upper st_dev.

	 * All lower layers that share the same fs as upper layer, use the same

	 * pseudo_dev as upper layer.  Allocate fs[0].pseudo_dev even for lower

	 * only overlay to simplify ovl_fs_free().

	 * is_lower will be set if upper fs is shared with a lower layer.

	 */

	err = get_anon_bdev(&ofs->fs[0].pseudo_dev);

	if (err) {

		pr_err("failed to get anonymous bdev for upper fs\n");

		goto out;

	}



	if (ofs->upper_mnt) {

		ofs->fs[0].sb = ofs->upper_mnt->mnt_sb;

		ofs->fs[0].pseudo_dev = ofs->upper_mnt->mnt_sb->s_dev;

		ofs->fs[0].is_lower = false;

	}

CRA Git | Maintained and supported by SUSTech CRA and CCSE