[Bug 197045] New: renameat2 rename_noreplace

[Bug 197045] New: renameat2 rename_noreplace

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=197045

            Bug ID: 197045
           Summary: renameat2 rename_noreplace
           Product: File System
           Version: 2.5
    Kernel Version: 4.4.0, 4.11.0
          Hardware: All
                OS: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: ext4
          Assignee: fs_ext4@kernel-bugs.osdl.org
          Reporter: martin@salbaba.co.at
        Regression: No

on ext4 renameat2 fails in conjunction with RENAME_NOREPLACE, if the target
file is not present

renameat2(AT_FDCWD, "rename-test-a", AT_FDCWD, "rename-test-c",
RENAME_NOREPLACE) = -1 EINVAL (Invalid argument)

if the target file is present, functionality is ok

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[Bug 197045] renameat2 rename_noreplace

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https://bugzilla.kernel.org/show_bug.cgi?id=197045

--- Comment #1 from Martin Salbba (martin@salbaba.co.at) ---
works with brtfs and xfs

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[Bug 197045] renameat2 rename_noreplace

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Elvis Stansvik (elvstone@gmail.com) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |elvstone@gmail.com

--- Comment #2 from Elvis Stansvik (elvstone@gmail.com) ---
Created attachment 260359
  --> https://bugzilla.kernel.org/attachment.cgi?id=260359&action=edit
Test case showing the problem

A test case, run with a.out <srcfile> <dstfile>

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[Bug 197045] renameat2 rename_noreplace

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https://bugzilla.kernel.org/show_bug.cgi?id=197045

--- Comment #3 from Elvis Stansvik (elvstone@gmail.com) ---
I'm hit by this on 4.10 a well (the default kernel on Ubuntu 16.04).

I attached a full test case showing.

Example run:


> [estan@newton renameat2tc]$ gcc renameat2.c 
> [estan@newton renameat2tc]$ touch foo
> [estan@newton renameat2tc]$ ./a.out foo bar
> Invalid argument
> [estan@newton renameat2tc]$ uname -a
> Linux newton 4.10.0-37-generic #41~16.04.1-Ubuntu SMP Fri Oct 6 22:42:59 UTC
> 2017 x86_64 x86_64 x86_64 GNU/Linux
> [estan@newton renameat2tc]$ mount | grep " / "
> /dev/sda1 on / type ext4 (rw,noatime,discard,errors=remount-ro,data=ordered)

The reason I discovered it was that Qt recently started using this syscall,
which in turn made Qt Creator (a Qt application) fail to write its config
files.

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[Bug 197045] renameat2 rename_noreplace

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Thiago Macieira (thiago@macieira.org) changed:

           What    |Removed                     |Added
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                 CC|                            |thiago@macieira.org

--- Comment #4 from Thiago Macieira (thiago@macieira.org) ---
Martin: can you confirm you did see these issues on 4.4 and 4.11? Elvis is
reporting he did not see the issue on 4.4.

By any chance, are you also on Ubuntu?

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[Bug 197045] renameat2 rename_noreplace

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--- Comment #5 from Elvis Stansvik (elvstone@gmail.com) ---
Martin: I've just discovered that I only see this problem when on my eCryptfs
encrypted home directory, not when testing in e.g. /tmp (unencrypted). Are you
also using eCryptfs?

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[Bug 197045] renameat2 rename_noreplace

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--- Comment #6 from Elvis Stansvik (elvstone@gmail.com) ---
So I guess I'm hitting this:
https://github.com/torvalds/linux/blob/master/fs/ecryptfs/inode.c#L592

Seems rename flags are not supported on ecryptfs, plain and simple?

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[Bug 197045] renameat2 rename_noreplace

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--- Comment #7 from Elvis Stansvik (elvstone@gmail.com) ---
Here's the patch that added the if (flags) return EINVAL; for ecryptfs:

https://patchwork.kernel.org/patch/9295699/

So I guess it's just expected that it won't work on ecryptfs.

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[Bug 197045] renameat2 rename_noreplace

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--- Comment #8 from Elvis Stansvik (elvstone@gmail.com) ---
Though I wonder if that is correct, or if it was hastily added by mistake for
ecryptfs as part of that mass porting to rename2.. Maybe it would just work if
ecryptfs_rename simply forwarded the flags to vfs_rename without checking
them..? Someone who knows the code will have to answer.

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[Bug 197045] renameat2 rename_noreplace

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--- Comment #9 from Elvis Stansvik (elvstone@gmail.com) ---
Scratch that, it's obviously not that easy.

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[Bug 197045] renameat2 rename_noreplace

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--- Comment #10 from Thiago Macieira (thiago@macieira.org) ---
No, it seems that non-local filesystems need specific code to guarante
RENAME_NOREPLACE, so the EINVAL error is legitimate.

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[Bug 197045] renameat2 rename_noreplace

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Theodore Tso (tytso@mit.edu) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
                 CC|                            |tytso@mit.edu
         Resolution|---                         |INVALID

--- Comment #11 from Theodore Tso (tytso@mit.edu) ---
I've confirmed that the test case works just fine on plain ext4, using the 4.13
based kernel.  I've also confirmed that it works just fine if you use ext4
encryption.  (I suggest that Ubuntu users file a feature request bug to Ubuntu
to ditch ecryptfs and switch to ext4 encryption.)

I can also confirm that ecryptfs != ext4, and that discussing this here has
approximately zero chance of it being noticed by the ecryptfs maintainer.  
Since Tyler works at Canonical, filing a Launchpad bug is most likely to get
someone to look at it.

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[Bug 197045] renameat2 rename_noreplace

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--- Comment #12 from Thiago Macieira (thiago@macieira.org) ---
Thanks Ted.

For the record, I'm applying a fix to the Qt code, since the error is
legitimate for non-local fs: https://codereview.qt-project.org/209385

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--- Comment #13 from Elvis Stansvik (elvstone@gmail.com) ---
Indeed, I'll file an LP bug and try to ping Tyler. Who knows, perhaps they're
already planning to switch to encrypted ext4 (thanks for testing that Ted).

And thanks to Thiago for being so quick with the Qt fix (I ran into this
behavior by way of Qt).

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[Bug 197045] renameat2 rename_noreplace

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--- Comment #14 from Theodore Tso (tytso@mit.edu) ---
Michael Halcrow (the original author of ecryptfs, and who has jokingly referred
to his work on ext4 encryption as his apology for ecryptfs :-) and I have
talked to Tyler about Ubuntu switching to ext4 encryption.   This is really
going to be a matter of prioritizing work at Canonical; so user feature
requests (especially requests from paying users :-) would be helpful.

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