On 2015-08-02 09:51:16, Richard Weinberger wrote: > Am 02.08.2015 um 03:03 schrieb Tyler Hicks: > > Thanks for the report and for the patch, Richard! > > > > On 2015-07-31 12:23:10, Richard Weinberger wrote: > >> Mounting the same lower path multiple times should not result > >> into multiple ecryptfs instances, otherwise ecryptfs gets confused. > >> > >> A command sequence of: > > > > An important detail that took me a while to realize is that /tmp should > > be tmpfs in order to trigger the warnings below. I was unable to > > reproduce the warnings with ext4 as the lower filesystem. > > Hmm, I saw it with UBIFS found that it triggers with tmpfs too. > I gave ext4 a quick try and yes, it behaves differently, I get > a EIO upon the second unlink(). > > >> $ mount -t ecryptfs /tmp/.secret /mnt_a/secret/ > >> $ mount -t ecryptfs /tmp/.secret /mnt_b/secret/ > >> $ mkdir -p /mnt_a/secret/xxx > >> $ mkdir -p /mnt_b/secret/xxx > > > > Note that the -p option is covering up the fact that /mnt_b/secret/xxx > > already exists. Remove that option and you should see this error: > > > > mkdir: cannot create directory ‘/mnt_b/secret/xxx’: File exists > > > > This really isn't important other than understanding that the second > > mkdir it isn't needed. > > > >> $ echo foo > /mnt_a/secret/xxx/test.txt > >> $ echo foo > /mnt_b/secret/xxx/test.txt > > > > /mnt_b/secret/xxx/test.txt should already exist (it does for me, at > > least) so the same file is being written to twice in a row. Again, not > > really important other than to know that it isn't needed. > > > >> $ rm -rf /mnt_a/secret/xxx > >> $ rm -rf /mnt_b/secret/xxx > > > > The /mnt_b/secret/xxx dcache entry is stale here because the underlying > > file was removed by the first rm command in the /mnt_a/secret mount. The > > lower inode's nlink is 0 at this point and what should be happening > > here, I think, is that the eCryptfs dentry should be invalidated and the > > eCryptfs inode should be destroyed. > > > > I think that the proper fix is to catch this condition in > > ecryptfs_d_revalidate(). I've started working on coming up with a patch > > for that but I'll need some more time to finish and test it. > > So ecryptfs definitely supports mounting the same lower path multiple times? > What is the benefit of that behavior? No, it doesn't support that in a way that provides consistency among all of the eCryptfs mounts. However, multiple mounts on the same lower path is not the cause of this bug. The real issue is a stale dcache entry when the lower filesystem has been modified without eCryptfs' knowing. I can trigger the same warnings with only a single eCryptfs mount. Tyler > > Thanks, > //richard
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