Re: [PATCH] ceph: make sure directories aren't complete after setting crypt context

["Luís Henriques" <lhenriques@suse.de>]

Xiubo Li <xiubli@redhat.com> writes:

> On 18/11/2022 02:02, Luís Henriques wrote:
>> Xiubo Li <xiubli@redhat.com> writes:
>>
>>> On 17/11/2022 16:03, Xiubo Li wrote:
>>>> On 16/11/2022 23:37, Luís Henriques wrote:
>>>>> When setting a directory's crypt context, __ceph_dir_clear_complete() needs
>>>>> to be used otherwise, if it was complete before, any old dentry that's still
>>>>> around will be valid.
>>>>>
>>>>> Signed-off-by: Luís Henriques <lhenriques@suse.de>
>>>>> ---
>>>>> Hi!
>>>>>
>>>>> Here's a simple way to trigger the bug this patch is fixing:
>>>>>
>>>>> # cd /cephfs
>>>>> # ls mydir
>>>>> nKRhofOAVNsAwVLvDw7a0c9ypsjbZfK3n0Npnmni6j0
>>>>> # ls mydir/nKRhofOAVNsAwVLvDw7a0c9ypsjbZfK3n0Npnmni6j0/
>>>>> Cyuer5xT+kBlEPgtwAqSj0WK2taEljP5vHZ,D8VXCJ8
>>>>> u+46b2XVCt7Obpz0gznZyNLRj79Q2l4KmkwbKOzdQKw
>>>>> # fscrypt unlock mydir
>>>>> # touch /mnt/test/mydir/mysubdir/file
>>>>> touch: cannot touch '/mnt/test/mydir/mysubdir/file': No such file or
>>>>> directory
>>>>>
>>>>>    fs/ceph/crypto.c | 4 ++++
>>>>>    1 file changed, 4 insertions(+)
>>>>>
>>>>> diff --git a/fs/ceph/crypto.c b/fs/ceph/crypto.c
>>>>> index 35a2ccfe6899..dc1557967032 100644
>>>>> --- a/fs/ceph/crypto.c
>>>>> +++ b/fs/ceph/crypto.c
>>>>> @@ -87,6 +87,10 @@ static int ceph_crypt_get_context(struct inode *inode,
>>>>> void *ctx, size_t len)
>>>>>            return -ERANGE;
>>>>>          memcpy(ctx, cfa->cfa_blob, ctxlen);
>>>>> +
>>>>> +    /* Directory isn't complete anymore */
>>>>> +    if (S_ISDIR(inode->i_mode) && __ceph_dir_is_complete(ci))
>>>>> +        __ceph_dir_clear_complete(ci);
>>>> Hi Luis,
>>>>
>>>> Good catch!
>>>>
>>>> BTW, why do this in the ceph_crypt_get_context() ? As my understanding is that
>>>> we should mark 'mydir' as incomplete when unlocking it. While as I remembered
>>>> the unlock operation will do:
>>>>
>>>>
>>>> Step1: get_encpolicy via 'mydir' as ctx
>>>> Step2: rm_enckey of ctx from the superblock
>>>>
>>> Sorry, it should be add_enckey.
>>>> Since I am still running the test cases for the file lock patches, so I didn't
>>>> catch logs to confirm the above steps yet.
>>>>
>>>> If I am right IMO then we should mark the dir as incomplete in the Step2
>>>> instead, because for non-unlock operations they may also do the Step1.
>>>>
>>> Your patch will work. But probably we should do this just around
>>> __fscrypt_prepare_readdir() or fscrypt_prepare_readdir() instead ? We need to
>>> detect that once the 'inode->i_crypt_info' changed then mark the dir as
>>> incomplete.
>>>
>>> For now for the lock operation it will evict the inode, which will help do this
>>> for us already. But for unlock case, we need to handle it by ourself.
>> OK, that makes sense and to be honest I thought that there should be
>> another place for doing this. Unfortunately, I didn't found it: in the
>> test case I have the fscrypt_prepare_readdir() isn't called:
>>
>>     # cd /cephfs
>>     # ls mydir
>>     nKRhofOAVNsAwVLvDw7a0c9ypsjbZfK3n0Npnmni6j0
>>     # ls mydir/nKRhofOAVNsAwVLvDw7a0c9ypsjbZfK3n0Npnmni6j0/
>>     Cyuer5xT+kBlEPgtwAqSj0WK2taEljP5vHZ,D8VXCJ8 u+46b2XVCt7Obpz0gznZyNLRj79Q2l4KmkwbKOzdQKw
>>
>> At this point readdir was executed, of course.  And
>> __ceph_dir_set_complete() is also used to indicate that we have the full
>> contents.  However, executing the following commands won't result in any
>> new readdir():
>>
>>     # fscrypt unlock mydir
>>     # touch /mnt/test/mydir/mysubdir/file
>>
>> and since the encryption key is set at the sb level, I couldn't find a way
>> to detect changes in inode->i_crypt_info.  ceph_d_revalidate() is invoked
>> but at that point I don't thing we have a way to know what is changing.
>>
>> Any ideas?
>
> # ls mydir/
> zy94Zt01M90xwYq+nxJsEvea+HYq49mqVgrUBkYrJAU
> # ls mydir/zy94Zt01M90xwYq+nxJsEvea+HYq49mqVgrUBkYrJAU/
> 24iNa8ICYc6nZZIkL,4n1sOtp9KiaTGtpq8PCZDQ6LU
> ivG4rQYzg6YENagbTZaV2kh2sVouEdlkmBZPfgVDl48
>
> I have added the debug logs in all the places just like:
>
> @@ -784,7 +786,9 @@ static struct dentry *ceph_lookup(struct inode *dir, struct
> dentry *dentry,
>                 return ERR_PTR(-ENAMETOOLONG);
>
>         if (IS_ENCRYPTED(dir)) {
> +       printk("%s fscrypt_has_encryption_key(dir): %d ======\n", __func__,
> fscrypt_has_encryption_key(dir));
>                 err = __fscrypt_prepare_readdir(dir);
> +       printk("%s fscrypt_has_encryption_key(dir): %d ======\n", __func__,
> fscrypt_has_encryption_key(dir));
>                 if (err)
>                         return ERR_PTR(err);
>                 if (!fscrypt_has_encryption_key(dir)) {
>
>
> # fscrypt unlock mydir
> Enter custom passphrase for protector "l":
> "mydir" is now unlocked and ready for use.
>
> And after "mydir/" was unlocked and then when doing:
>
> # touch mydir/dir/file2
>
> And when lookup the "dir/" dentry I can see the "mydir/" encryption key changed:
>
> 709 <7>[79125.023676] ceph:  __ceph_caps_issued_mask ino 0x10000000004 cap
> 000000004dc11892 issued pAsLsXsFs (mask As)
> 710 <7>[79125.023687] ceph:  __touch_cap 000000007071b095 cap 000000004dc11892
> mds0
> 711 <7>[79125.023823] ceph:  lookup 000000007071b095 dentry 00000000f97501b2
> 'dir'
> 712 <4>[79125.023838] ceph_lookup fscrypt_has_encryption_key(dir): 0 ======
> 713 <4>[79125.024186] ceph_lookup fscrypt_has_encryption_key(dir): 1 ======
> 714 <7>[79125.024194] ceph:   dir 000000007071b095 flags are 0x0
> 715 <7>[79125.024269] ceph:  do_request on 00000000a93fafef
>
> I am thinking could we just make __fscrypt_prepare_readdir(), which will return
> 0 when the key is already set or successfully set, to return 1 instead of 0 to
> mark that the key changed ?

OK, I see what you mean.  Thanks.  What about simply detect this change
here instead of changing __fscrypt_prepare_readdir() semantics?  Because I
think that would require changes in several other places, including other
filesystems.

What about something like this?

diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c
index edc2bf0aab83..499ec75d2496 100644
--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -784,6 +784,8 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
 		return ERR_PTR(-ENAMETOOLONG);
 
 	if (IS_ENCRYPTED(dir)) {
+		bool had_key = fscrypt_has_encryption_key(dir);
+
 		err = __fscrypt_prepare_readdir(dir);
 		if (err)
 			return ERR_PTR(err);
@@ -791,6 +793,8 @@ static struct dentry *ceph_lookup(struct inode *dir, struct dentry *dentry,
 			spin_lock(&dentry->d_lock);
 			dentry->d_flags |= DCACHE_NOKEY_NAME;
 			spin_unlock(&dentry->d_lock);
+		} else if (!had_key) {
+			__ceph_dir_clear_complete(ceph_inode(dir));
 		}
 	}
 
Cheers,
-- 
Luís