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Wed, 8 Mar 2023 18:30:58 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id EPQIBGLUCGTpdAAAMHmgww (envelope-from ); Wed, 08 Mar 2023 18:30:58 +0000 Received: from localhost (brahms.olymp [local]) by brahms.olymp (OpenSMTPD) with ESMTPA id 47827059; Wed, 8 Mar 2023 18:30:57 +0000 (UTC) From: =?utf-8?Q?Lu=C3=ADs_Henriques?= To: Jeff Layton Cc: Xiubo Li , idryomov@gmail.com, ceph-devel@vger.kernel.org, vshankar@redhat.com, mchangir@redhat.com Subject: Re: [PATCH v16 25/68] ceph: make d_revalidate call fscrypt revalidator for encrypted dentries References: <20230227032813.337906-1-xiubli@redhat.com> <20230227032813.337906-26-xiubli@redhat.com> <87o7p48kby.fsf@suse.de> <72e7b6cc-ba6b-796e-2ff6-1e8ff2ac7eee@redhat.com> <87jzzr8ubv.fsf@suse.de> <30b9604e-d5fa-7191-5743-b7b5e72acd6b@redhat.com> <87fsaf88sc.fsf@suse.de> <406dc339c219d98639b752342136461f5070f259.camel@kernel.org> Date: Wed, 08 Mar 2023 18:30:57 +0000 In-Reply-To: <406dc339c219d98639b752342136461f5070f259.camel@kernel.org> (Jeff Layton's message of "Wed, 08 Mar 2023 12:54:43 -0500") Message-ID: <871qlz859a.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org Jeff Layton writes: > On Wed, 2023-03-08 at 17:14 +0000, Lu=C3=ADs Henriques wrote: >> Xiubo Li writes: >>=20 >> > On 08/03/2023 17:29, Lu=C3=ADs Henriques wrote: >> > > Xiubo Li writes: >> > >=20 >> > > > On 08/03/2023 02:53, Lu=C3=ADs Henriques wrote: >> > > > > xiubli@redhat.com=C2=A0writes: >> > > > >=20 >> > > > > > From: Jeff Layton >> > > > > >=20 >> > > > > > If we have a dentry which represents a no-key name, then we ne= ed to test >> > > > > > whether the parent directory's encryption key has since been a= dded.=C2=A0 Do >> > > > > > that before we test anything else about the dentry. >> > > > > >=20 >> > > > > > Reviewed-by: Xiubo Li >> > > > > > Signed-off-by: Jeff Layton >> > > > > > --- >> > > > > > =C2=A0=C2=A0=C2=A0 fs/ceph/dir.c | 8 ++++++-- >> > > > > > =C2=A0=C2=A0=C2=A0 1 file changed, 6 insertions(+), 2 deletion= s(-) >> > > > > >=20 >> > > > > > diff --git a/fs/ceph/dir.c b/fs/ceph/dir.c >> > > > > > index d3c2853bb0f1..5ead9f59e693 100644 >> > > > > > --- a/fs/ceph/dir.c >> > > > > > +++ b/fs/ceph/dir.c >> > > > > > @@ -1770,6 +1770,10 @@ static int ceph_d_revalidate(struct den= try *dentry, unsigned int flags) >> > > > > > =C2=A0=C2=A0=C2=A0=C2=A0 struct inode *dir, *inode; >> > > > > > =C2=A0=C2=A0=C2=A0=C2=A0 struct ceph_mds_client *mdsc; >> > > > > > =C2=A0=C2=A0=C2=A0 + valid =3D fscrypt_d_revalidate(dentry, fl= ags); >> > > > > > + if (valid <=3D 0) >> > > > > > + return valid; >> > > > > > + >> > > > > This patch has confused me in the past, and today I found myself >> > > > > scratching my head again looking at it. >> > > > >=20 >> > > > > So, I've started seeing generic/123 test failing when running it= with >> > > > > test_dummy_encryption.=C2=A0 I was almost sure that this test us= ed to run fine >> > > > > before, but I couldn't find any evidence (somehow I lost my old = testing >> > > > > logs...). >> > > > >=20 >> > > > > Anyway, the test is quite simple: >> > > > >=20 >> > > > > 1. Creates a directory with write permissions for root only >> > > > > 2. Writes into a file in that directory >> > > > > 3. Uses 'su' to try to modify that file as a different user, and >> > > > > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 gets -EPERM >> > > > >=20 >> > > > > All these steps run fine, and the test should pass.=C2=A0 *Howev= er*, in the >> > > > > test cleanup function, a simple 'rm -rf ' will fail with -E= NOTEMPTY. >> > > > > 'strace' shows that calling unlinkat() to remove the file got a = '-ENOENT' >> > > > > and then -ENOTEMPTY for the directory. >> > > > >=20 >> > > > > Some digging allowed me to figure out that running commands with= 'su' will >> > > > > drop caches (I see 'su (874): drop_caches: 2' in the log).=C2=A0= And this is >> > > > > how I ended up looking at this patch.=C2=A0 fscrypt_d_revalidate= () will return >> > > > > '0' if the parent directory does has a key (fscrypt_has_encrypti= on_key()). >> > > > > Can we really say here that the dentry is *not* valid in that ca= se?=C2=A0 Or >> > > > > should that '<=3D 0' be a '< 0'? >> > > > >=20 >> > > > > (But again, this patch has confused me before...) >> > > > Luis, >> > > >=20 >> > > > Could you reproduce it with the latest testing branch ? >> > > Yes, I'm seeing this with the latest code. >> >=20 >> > Okay. That's odd. >> >=20 >> > BTW, are you using the non-root user to run the test ? >> >=20 >> > Locally I am using the root user and still couldn't reproduce it. >>=20 >> Yes, I'm running the tests as root but I've also 'fsgqa' user in the >> system (which is used by this test.=C2=A0 Anyway, for reference, here's = what >> I'm using in my fstests configuration: >>=20 >> TEST_FS_MOUNT_OPTS=3D"-o name=3Dadmin,secret=3D,copyfrom,ms_mode=3D= crc,test_dummy_encryption" >> MOUNT_OPTIONS=3D"-o name=3Dadmin,secret=3D,copyfrom,ms_mode=3Dcrc,t= est_dummy_encryption" >>=20 >> > >=20 >> > > > I never seen the generic/123 failure yet. And just now I ran the t= est for many >> > > > times locally it worked fine. >> > > That's odd.=C2=A0 With 'test_dummy_encryption' mount option I can re= produce it >> > > every time. >> > >=20 >> > > > =C2=A0 From the generic/123 test code it will never touch the key = while testing, that >> > > > means the dentries under the test dir will always have the keyed n= ame. And then >> > > > the 'fscrypt_d_revalidate()' should return 1 always. >> > > >=20 >> > > > Only when we remove the key will it trigger evicting the inodes an= d then when we >> > > > add the key back will the 'fscrypt_d_revalidate()' return 0 by che= cking the >> > > > 'fscrypt_has_encryption_key()'. >> > > >=20 >> > > > As I remembered we have one or more fixes about this those days, n= ot sure >> > > > whether you were hitting those bugs we have already fixed ? >> > > Yeah, I remember now, and I guess there's yet another one here! >> > >=20 >> > > I'll look closer into this and see if I can find out something else.= =C2=A0 I'm >> > > definitely seeing 'fscrypt_d_revalidate()' returning 0, so probably = the >> > > bug is in the error paths, when the 'fsgqa' user tries to write into= the >> > > file. >> >=20 >> > Please add some debug logs in the code. >>=20 >> I *think* I've something.=C2=A0 The problem seems to be that, after the >> drop_caches, the test directory is evicted and ceph_evict_inode() will >> call fscrypt_put_encryption_info().=C2=A0 This last function will clear = the >> inode fscrypt info.=C2=A0 Later on, when the test tries to write to the = file >> with: >>=20 >> =C2=A0 _user_do "echo goo >> $my_test_subdir/data_coherency.txt" >>=20 >> function ceph_atomic_open() will correctly identify that '$my_test_subdi= r' >> is encrypted, but the key isn't set because the inode was evicted.=C2=A0= This >> means that fscrypt_has_encryption_key() will return '0' and DCACHE_NOKEY= _NAME >> will be *incorrectly* added to the 'data_coherency.txt' dentry flags. >>=20 >> Later on, ceph_d_revalidate() will see the problem I initially described. >>=20 >> The (RFC) patch bellow seems to fix the issue.=C2=A0 Basically, it will = force >> the fscrypt info to be set in the directory by calling __fscrypt_prepare= _readdir() >> and the fscrypt_has_encryption_key() will then return 'true'. >>=20 > > >> Cheers >> -- >> Lu=C3=ADs >>=20 >> diff --git a/fs/ceph/file.c b/fs/ceph/file.c >> index dee3b445f415..3f2df84a6323 100644 >> --- a/fs/ceph/file.c >> +++ b/fs/ceph/file.c >> @@ -795,7 +795,8 @@ int ceph_atomic_open(struct inode *dir, struct dentr= y *dentry, >> =C2=A0 ihold(dir); >> =C2=A0 if (IS_ENCRYPTED(dir)) { >> =C2=A0 set_bit(CEPH_MDS_R_FSCRYPT_FILE, &req->r_req_flags); >> - if (!fscrypt_has_encryption_key(dir)) { >> + err =3D __fscrypt_prepare_readdir(dir); > > I want to say that i had something like this in place during an earlier > version of this series, but for different reasons. I think I convinced > myself later though that it wasn't needed? Oh well... Ah, good to know it _may_ make sense :-) >> + if (err || (!err && !fscrypt_has_encryption_key(dir))) { >> =C2=A0 spin_lock(&dentry->d_lock); >> =C2=A0 dentry->d_flags |=3D DCACHE_NOKEY_NAME; >> =C2=A0 spin_unlock(&dentry->d_lock); > > Once an inode is evicted, my understanding was that it won't end up > being used anymore. It's on its way out of the cache and it's not hashed > anymore at that point. > > How does a new atomic open after drop_caches end up with the inode > struct that existed before it? Hmm... so, I *think* that what's happening is that it is a new inode but the key is still available. Looking at the code it seems that fscrypt will get the context (->get_context()) from ceph code and then fscrypt_setup_encryption_info() should initialize everything in the inode. And at that point fscrypt_has_encryption_key() will finally return 'true'. Does this make sense? Cheers, --=20 Lu=C3=ADs