Re: [RFC PATCH v5 20/19] ceph: make ceph_get_name decrypt filenames

Luis Henriques
2021-04-01T11:14:30Z

On Wed, Mar 31, 2021 at 04:35:20PM -0400, Jeff Layton wrote:
> When we do a lookupino to the MDS, we get a filename in the trace.
> ceph_get_name uses that name directly, so we must properly decrypt
> it before copying it to the name buffer.
>
> Signed-off-by: Jeff Layton <jlayton@kernel.org>
> ---
> fs/ceph/export.c | 42 +++++++++++++++++++++++++++++++-----------
> 1 file changed, 31 insertions(+), 11 deletions(-)
>
> This patch is what's needed to fix the "busy inodes after umount"
> issue I was seeing with xfstest generic/477, and also makes that
> test pass reliably with mounts using -o test_dummy_encryption.

You mentioned this issue the other day on IRC but I couldn't reproduce.

On the other hand, I'm seeing another issue. Here's a way to reproduce:

- create an encrypted dir 'd' and create a file 'f'
- umount and mount the filesystem
- unlock dir 'd'
- cat d/f
cat: d/2: No such file or directory

It happens _almost_ every time I do the umount+mount+unlock+cat. Looks
like ceph_atomic_open() fails to see that directory as encrypted. I don't
think the problem is on this open itself, but in the unlock because a
simple 'ls' also fails to show the decrypted names. (On the other end, if
you do an 'ls' _before_ the unlock, everything seems to work fine.)

I didn't had time to dig deeper into this yet, but I don't remember seeing
this behaviour in previous versions of the patchset.

Cheers,
--
Luís

>
> diff --git a/fs/ceph/export.c b/fs/ceph/export.c
> index 17d8c8f4ec89..f4e3a17ffc01 100644
> --- a/fs/ceph/export.c
> +++ b/fs/ceph/export.c
> @@ -7,6 +7,7 @@
>
> #include "super.h"
> #include "mds_client.h"
> +#include "crypto.h"
>
> /*
> * Basic fh
> @@ -516,7 +517,9 @@ static int ceph_get_name(struct dentry *parent, char *name,
> {
> struct ceph_mds_client *mdsc;
> struct ceph_mds_request *req;
> + struct inode *dir = d_inode(parent);
> struct inode *inode = d_inode(child);
> + struct ceph_mds_reply_info_parsed *rinfo;
> int err;
>
> if (ceph_snap(inode) != CEPH_NOSNAP)
> @@ -528,29 +531,46 @@ static int ceph_get_name(struct dentry *parent, char *name,
> if (IS_ERR(req))
> return PTR_ERR(req);
>
> - inode_lock(d_inode(parent));
> -
> + inode_lock(dir);
> req->r_inode = inode;
> ihold(inode);
> req->r_ino2 = ceph_vino(d_inode(parent));
> - req->r_parent = d_inode(parent);
> + req->r_parent = dir;
> set_bit(CEPH_MDS_R_PARENT_LOCKED, &req->r_req_flags);
> req->r_num_caps = 2;
> err = ceph_mdsc_do_request(mdsc, NULL, req);
> + inode_unlock(dir);
>
> - inode_unlock(d_inode(parent));
> + if (err)
> + goto out;
>
> - if (!err) {
> - struct ceph_mds_reply_info_parsed *rinfo = &req->r_reply_info;
> + rinfo = &req->r_reply_info;
> + if (!IS_ENCRYPTED(dir)) {
> memcpy(name, rinfo->dname, rinfo->dname_len);
> name[rinfo->dname_len] = 0;
> - dout("get_name %p ino %llx.%llx name %s\n",
> - child, ceph_vinop(inode), name);
> } else {
> - dout("get_name %p ino %llx.%llx err %d\n",
> - child, ceph_vinop(inode), err);
> - }
> + struct fscrypt_str oname = FSTR_INIT(NULL, 0);
> + struct ceph_fname fname = { .dir = dir,
> + .name = rinfo->dname,
> + .ctext = rinfo->altname,
> + .name_len = rinfo->dname_len,
> + .ctext_len = rinfo->altname_len };
> +
> + err = ceph_fname_alloc_buffer(dir, &oname);
> + if (err < 0)
> + goto out;
>
> + err = ceph_fname_to_usr(&fname, NULL, &oname, NULL);
> + if (!err) {
> + memcpy(name, oname.name, oname.len);
> + name[oname.len] = 0;
> + }
> + ceph_fname_free_buffer(dir, &oname);
> + }
> +out:
> + dout("get_name %p ino %llx.%llx err %d %s%s\n",
> + child, ceph_vinop(inode), err,
> + err ? "" : "name ", err ? "" : name);
> ceph_mdsc_put_request(req);
> return err;
> }
> --
> 2.30.2
>