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SubjectRe: [PATCH] ceph: fix memory leak in mount error path when using test_dummy_encryption
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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@suse.de>
>>>>> ---
>>>>> 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
>

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