cachefiles: Allow the cache to be non-root

Set mode 0600 on files in the cache so that cachefilesd can run as an
unprivileged user rather than leaving the files all with 0.  Directories
are already set to 0700.

Userspace then needs to set the uid and gid before issuing the "bind"
command and the cache must've been chown'd to those IDs.

Signed-off-by: David Howells <dhowells@redhat.com>
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
cc: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-erofs@lists.ozlabs.org
cc: linux-fsdevel@vger.kernel.org
Message-Id: <1853230.1684516880@warthog.procyon.org.uk>
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/cachefiles/namei.c b/fs/cachefiles/namei.c
index 82219a8f608427489ce6c0de8ed2e7060e4634de..66482c193e86a999f6dbe4dd0bc73c04200f14c1 100644 (file)
--- a/fs/cachefiles/namei.c
+++ b/fs/cachefiles/namei.c
@@ -451,7 +451,8 @@ struct file *cachefiles_create_tmpfile(struct cachefiles_object *object)
 
        ret = cachefiles_inject_write_error();
        if (ret == 0) {
-               file = vfs_tmpfile_open(&nop_mnt_idmap, &parentpath, S_IFREG,
+               file = vfs_tmpfile_open(&nop_mnt_idmap, &parentpath,
+                                       S_IFREG | 0600,
                                        O_RDWR | O_LARGEFILE | O_DIRECT,
                                        cache->cache_cred);
                ret = PTR_ERR_OR_ZERO(file);