Xiubo Li <xiubli@xxxxxxxxxx> writes: > On 09/03/2023 01:14, Luís Henriques wrote: >> Xiubo Li <xiubli@xxxxxxxxxx> writes: >> >>> On 08/03/2023 17:29, Luís Henriques wrote: >>>> Xiubo Li <xiubli@xxxxxxxxxx> writes: >>>> >>>>> On 08/03/2023 02:53, Luís Henriques wrote: >>>>>> xiubli@xxxxxxxxxx writes: >>>>>> >>>>>>> From: Jeff Layton <jlayton@xxxxxxxxxx> >>>>>>> >>>>>>> If we have a dentry which represents a no-key name, then we need to test >>>>>>> whether the parent directory's encryption key has since been added. Do >>>>>>> that before we test anything else about the dentry. >>>>>>> >>>>>>> Reviewed-by: Xiubo Li <xiubli@xxxxxxxxxx> >>>>>>> Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx> >>>>>>> --- >>>>>>> fs/ceph/dir.c | 8 ++++++-- >>>>>>> 1 file changed, 6 insertions(+), 2 deletions(-) >>>>>>> >>>>>>> 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 dentry *dentry, unsigned int flags) >>>>>>> struct inode *dir, *inode; >>>>>>> struct ceph_mds_client *mdsc; >>>>>>> + valid = fscrypt_d_revalidate(dentry, flags); >>>>>>> + if (valid <= 0) >>>>>>> + return valid; >>>>>>> + >>>>>> This patch has confused me in the past, and today I found myself >>>>>> scratching my head again looking at it. >>>>>> >>>>>> So, I've started seeing generic/123 test failing when running it with >>>>>> test_dummy_encryption. I was almost sure that this test used to run fine >>>>>> before, but I couldn't find any evidence (somehow I lost my old testing >>>>>> logs...). >>>>>> >>>>>> Anyway, the test is quite simple: >>>>>> >>>>>> 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 >>>>>> gets -EPERM >>>>>> >>>>>> All these steps run fine, and the test should pass. *However*, in the >>>>>> test cleanup function, a simple 'rm -rf <dir>' will fail with -ENOTEMPTY. >>>>>> 'strace' shows that calling unlinkat() to remove the file got a '-ENOENT' >>>>>> and then -ENOTEMPTY for the directory. >>>>>> >>>>>> 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). And this is >>>>>> how I ended up looking at this patch. fscrypt_d_revalidate() will return >>>>>> '0' if the parent directory does has a key (fscrypt_has_encryption_key()). >>>>>> Can we really say here that the dentry is *not* valid in that case? Or >>>>>> should that '<= 0' be a '< 0'? >>>>>> >>>>>> (But again, this patch has confused me before...) >>>>> Luis, >>>>> >>>>> Could you reproduce it with the latest testing branch ? >>>> Yes, I'm seeing this with the latest code. >>> Okay. That's odd. >>> >>> BTW, are you using the non-root user to run the test ? >>> >>> Locally I am using the root user and still couldn't reproduce it. >> Yes, I'm running the tests as root but I've also 'fsgqa' user in the >> system (which is used by this test. Anyway, for reference, here's what >> I'm using in my fstests configuration: >> >> TEST_FS_MOUNT_OPTS="-o name=admin,secret=<key>,copyfrom,ms_mode=crc,test_dummy_encryption" >> MOUNT_OPTIONS="-o name=admin,secret=<key>,copyfrom,ms_mode=crc,test_dummy_encryption" >> >>>>> I never seen the generic/123 failure yet. And just now I ran the test for many >>>>> times locally it worked fine. >>>> That's odd. With 'test_dummy_encryption' mount option I can reproduce it >>>> every time. >>>> >>>>> 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 name. And then >>>>> the 'fscrypt_d_revalidate()' should return 1 always. >>>>> >>>>> Only when we remove the key will it trigger evicting the inodes and then when we >>>>> add the key back will the 'fscrypt_d_revalidate()' return 0 by checking the >>>>> 'fscrypt_has_encryption_key()'. >>>>> >>>>> As I remembered we have one or more fixes about this those days, not sure >>>>> whether you were hitting those bugs we have already fixed ? >>>> Yeah, I remember now, and I guess there's yet another one here! >>>> >>>> I'll look closer into this and see if I can find out something else. 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. >>> Please add some debug logs in the code. >> I *think* I've something. 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(). This last function will clear the >> inode fscrypt info. Later on, when the test tries to write to the file >> with: >> >> _user_do "echo goo >> $my_test_subdir/data_coherency.txt" >> >> function ceph_atomic_open() will correctly identify that '$my_test_subdir' >> is encrypted, but the key isn't set because the inode was evicted. 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. >> >> Later on, ceph_d_revalidate() will see the problem I initially described. >> >> The (RFC) patch bellow seems to fix the issue. 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'. > > Interesting. > > It's worth to add one separated commit to fix this. > > Luis, could you send one patch to the mail list ? And please add the detail > comments in the code to explain it. > > This will help us to under stand the code and to debug potential similar bugs in > future. Sure, I'll do that. In fact, I'll probably send out two patches as Jeff also suggested a better name for __fscrypt_prepare_readdir(). Not sure Eric will take it, but it's worth trying. Cheers, -- Luís
