Re: [PATCH] ceph: fix memory leak in mount error path when using test_dummy_encryption

[Xiubo Li]

On 07/11/2022 22:19, Luís Henriques wrote:
> On Mon, Nov 07, 2022 at 07:06:40PM +0800, Xiubo Li wrote:
> > On 07/11/2022 18:23, Luís Henriques wrote:
> > > On Mon, Nov 07, 2022 at 03:47:23PM +0800, Xiubo Li wrote:
> > > > On 03/11/2022 23:36, Luís Henriques wrote:
> > > > > Because ceph_init_fs_context() will never be invoced in case we get a
> > > > > mount error, destroy_mount_options() won't be releasing fscrypt resources
> > > > > with fscrypt_free_dummy_policy().  This will result in a memory leak.  Add
> > > > > an invocation to this function in the mount error path.
> > > > >
> > > > > Signed-off-by: Luís Henriques <lhenriques@xxxxxxx>
> > > > > ---
> > > > >     fs/ceph/super.c | 1 +
> > > > >     1 file changed, 1 insertion(+)
> > > > >
> > > > > diff --git a/fs/ceph/super.c b/fs/ceph/super.c
> > > > > index 2224d44d21c0..6b9fd04b25cd 100644
> > > > > --- a/fs/ceph/super.c
> > > > > +++ b/fs/ceph/super.c
> > > > > @@ -1362,6 +1362,7 @@ static int ceph_get_tree(struct fs_context *fc)
> > > > >     	ceph_mdsc_close_sessions(fsc->mdsc);
> > > > >     	deactivate_locked_super(sb);
> > > > > +	fscrypt_free_dummy_policy(&fsc->fsc_dummy_enc_policy);
> > > > Hi Luis,
> > > >
> > > > BTW, any reason the following code won't be triggered ?
> > > >
> > > > deactivate_locked_super(sb);
> > > >
> > > >     --> fs->kill_sb(s);
> > > >
> > > >           --> ceph_kill_sb()
> > > >
> > > >                 --> kill_anon_super()
> > > >
> > > >                       --> generic_shutdown_super()
> > > >
> > > >                             --> sop->put_super()
> > > >
> > > >                                   --> ceph_put_super()
> > > >
> > > >                                         --> ceph_fscrypt_free_dummy_policy()
> > > >
> > > >                                              --> fscrypt_free_dummy_policy(
> > > Here's what I'm seeing here:
> > >
> > >     sys_mount->path_mount->do_new_mount->vfs_get_tree->ceph_get_tree
> > >
> > > ceph_get_tree() fails due to ceph_real_mount() returning an error.  My
> > > understanding is that that, since fc->root is never set, that code path
> > > will never be triggered.  Does that make sense?
> > Okay, you are right!
> >
> > How about fixing it in ceph_real_mount() instead ?
> Sure, I can send a patch for doing that instead.  However, my opinion is
> that it makes more sense to do it, mostly because ceph_get_tree() is
> already doing clean-up work on the error path (ceph_mdsc_close_sessions()
> and deactivate_locked_super()).
>
> But let me know if you really prefer doing in ceph_read_mount() and I'll
> send v2.

IMO it'd better to do this in ceph_real_mount(), which will make the 
code to be easier to read.

Thanks!

- Xiubo

> > > An easy way to reproduce is by running fstest ceph/005 with the
> > > 'test_dummy_encryption' option.  (I'll probably need to send a patch to
> > > disable this test when this option is present.)
> > Anyway this should be fixed in kceph.
> Yes, agreed.
>
> Cheers,
> --
> Luís