On Mon, Oct 31, 2022 at 05:15:51PM +0800, Xiubo Li wrote:
>
> On 27/10/2022 19:26, Luís Henriques wrote:
> > If a client doesn't have Fx caps on a directory, it will get errors while
> > trying encrypt it:
> >
> > ceph: handle_cap_grant: cap grant attempt to change fscrypt_auth on non-I_NEW inode (old len 0 new len 48)
> > fscrypt (ceph, inode 1099511627812): Error -105 getting encryption context
> >
> > A simple way to reproduce this is to use two clients:
> >
> > client1 # mkdir /mnt/mydir
> >
> > client2 # ls /mnt/mydir
> >
> > client1 # fscrypt encrypt /mnt/mydir
> > client1 # echo hello > /mnt/mydir/world
> >
> > This happens because, in __ceph_setattr(), we only initialize
> > ci->fscrypt_auth if we have Ax. If we don't have, we'll need to do that
> > later, in handle_cap_grant().
> >
> > Signed-off-by: Luís Henriques <lhenriques@xxxxxxx>
> > ---
> > Hi!
> >
> > To be honest, I'm not really sure about the conditions in the 'if': shall
> > I bother checking it's really a dir and that it is empty?
> >
> > Cheers,
> > --
> > Luís
> >
> > fs/ceph/caps.c | 26 +++++++++++++++++++++++---
> > 1 file changed, 23 insertions(+), 3 deletions(-)
> >
> > diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
> > index 443fce066d42..e33b5c276cf3 100644
> > --- a/fs/ceph/caps.c
> > +++ b/fs/ceph/caps.c
> > @@ -3511,9 +3511,29 @@ static void handle_cap_grant(struct inode *inode,
> > from_kuid(&init_user_ns, inode->i_uid),
> > from_kgid(&init_user_ns, inode->i_gid));
> > #if IS_ENABLED(CONFIG_FS_ENCRYPTION)
> > - if (ci->fscrypt_auth_len != extra_info->fscrypt_auth_len ||
> > - memcmp(ci->fscrypt_auth, extra_info->fscrypt_auth,
> > - ci->fscrypt_auth_len))
> > + if ((ci->fscrypt_auth_len == 0) &&
> > + (extra_info->fscrypt_auth_len > 0) &&
> > + S_ISDIR(inode->i_mode) &&
> > + (ci->i_rsubdirs + ci->i_rfiles == 1)) {
> > + /*
> > + * We'll get here when setting up an encrypted directory
> > + * but we don't have Fx in that directory, i.e. other
> > + * clients have accessed this directory too.
> > + */
> > + ci->fscrypt_auth = kmemdup(extra_info->fscrypt_auth,
> > + extra_info->fscrypt_auth_len,
> > + GFP_KERNEL);
> > + if (ci->fscrypt_auth) {
> > + inode->i_flags |= S_ENCRYPTED;
> > + ci->fscrypt_auth_len = extra_info->fscrypt_auth_len;
> > + } else {
> > + pr_err("Failed to alloc memory for %llx.%llx fscrypt_auth\n",
> > + ceph_vinop(inode));
> > + }
> > + dout("ino %llx.%llx is now encrypted\n", ceph_vinop(inode));
> > + } else if (ci->fscrypt_auth_len != extra_info->fscrypt_auth_len ||
> > + memcmp(ci->fscrypt_auth, extra_info->fscrypt_auth,
> > + ci->fscrypt_auth_len))
> > pr_warn_ratelimited("%s: cap grant attempt to change fscrypt_auth on non-I_NEW inode (old len %d new len %d)\n",
> > __func__, ci->fscrypt_auth_len, extra_info->fscrypt_auth_len);
> > #endif
>
> Hi Luis,
>
> Thanks for your time on this bug.
>
> IMO we should fix this in ceph_fill_inode():
>
> 995 #ifdef CONFIG_FS_ENCRYPTION
> 996 if (iinfo->fscrypt_auth_len && (inode->i_state & I_NEW)) {
> 997 kfree(ci->fscrypt_auth);
> 998 ci->fscrypt_auth_len = iinfo->fscrypt_auth_len;
> 999 ci->fscrypt_auth = iinfo->fscrypt_auth;
> 1000 iinfo->fscrypt_auth = NULL;
> 1001 iinfo->fscrypt_auth_len = 0;
> 1002 inode_set_flags(inode, S_ENCRYPTED, S_ENCRYPTED);
> 1003 }
> 1004 #endif
>
> The setattr will get a reply from MDS including the fscrypt auth info, I
> think the kclient just drop it here.
I've done some testing and I don't really see this code kfree'ing a valid
fscrypt_auth here. However, I guess it is possible to fix this issue here
too, but in a different way, by changing that 'if' condition to:
if (iinfo->fscrypt_auth_len &&
((inode->i_state & I_NEW) || (ci->fscrypt_auth_len == 0))) {
...
}
I'm not really sure if this is sane though. When we loose the 'Ax' caps
(another client as accessed the directory we're encrypting), we also seem
to loose the I_NEW state. Using the above code seems to work for the
testcase in my patch, but I'm not sure it won't break something else.
Cheers,
--
Luís
> If we fix it in handle_cap_grant() I am afraid this bug still exists. What
> if there is no any new caps will be issued or revoked recently and then
> access to the directory ?
>
> Thanks
>
> - Xiubo
>
> >
>
