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ovl: Modify ovl_lookup() and friends to lookup metacopy dentry

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This patch modifies ovl_lookup() and friends to lookup metacopy dentries.
It also allows for presence of metacopy dentries in lower layer.

During lookup, check for presence of OVL_XATTR_METACOPY and if not present,
set OVL_UPPERDATA bit in flags.

We don't support metacopy feature with nfs_export.  So in nfs_export code,
we set OVL_UPPERDATA flag set unconditionally if upper inode exists.

Do not follow metacopy origin if we find a metacopy only inode and metacopy
feature is not enabled for that mount.  Like redirect, this can have
security implications where an attacker could hand craft upper and try to
gain access to file on lower which it should not have to begin with.

Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Reviewed-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
This commit is contained in:
Vivek Goyal
2018-05-11 11:49:28 -04:00
committed by Miklos Szeredi
parent 027065b726
commit 9d3dfea3d3
5 changed files with 131 additions and 18 deletions
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22
fs/overlayfs/util.c
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@@ -778,3 +778,25 @@ err:
pr_err("overlayfs: failed to lock workdir+upperdir\n");
return -EIO;
}
/* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */
int ovl_check_metacopy_xattr(struct dentry *dentry)
{
int res;
/* Only regular files can have metacopy xattr */
if (!S_ISREG(d_inode(dentry)->i_mode))
return 0;
res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);
if (res < 0) {
if (res == -ENODATA || res == -EOPNOTSUPP)
return 0;
goto out;
}
return 1;
out:
pr_warn_ratelimited("overlayfs: failed to get metacopy (%i)\n", res);
return res;
}