Re: [PATCH 1/2] src/vfs: probe O_TMPFILE support on the base mount in the idmapped tests

在 2026/8/13 01:26, Zorro Lang 写道:
> On Mon, Jul 20, 2026 at 06:15:31PM +0930, Qu Wenruo wrote:
>>
>>
>> 在 2026/6/16 01:03, Christian Brauner 写道:
>>> openat_tmpfile_supported() in the idmapped mount tests probes O_TMPFILE
>>> on the idmapped mount (open_tree_fd) as the test's fsuid -- but that
>>> fsuid is not mapped by the idmapped mount under test, so it really asks
>>> "can this unmapped caller create a tmpfile through this idmap?" instead
>>> of "does the filesystem support O_TMPFILE?".
>>>
>>> On overlayfs this is a false negative: the backing tmpfile ends up owned
>>> by an unmapped id, overlayfs opens it with O_NOATIME and may_open()
>>> returns -EPERM, so the tmpfile sub-tests are wrongly skipped.
>>>
>>> O_TMPFILE support is a property of the filesystem, not of the idmapped
>>> mount or the caller's mapping. Probe info->t_dir1_fd, the base mount
>>> that the caller owns, exactly as the non-idmapped setgid tests already
>>> do. The probe then succeeds on every filesystem and the tmpfile
>>> sub-tests run as the mapped fsuid.
>>>
>>> Signed-off-by: Christian Brauner (Amutable) <[email protected]>
>>
>> Reviewed-by: Qu Wenruo <[email protected]>
>>
>> Furthermore, since kernel commit 539dce114465 ("fs: refuse O_TMPFILE
>> creation with an unmapped fsuid or fsgid"), even without overlayfs the
>> involved tests will fail due to the extra checks.
>>
>> So this is not only affecting overlayfs but all regular fses now.
>>
>> I hope we can at least merge this one asap.
> 
> Hi Wenruo,
> 
> Before merging this patch, I've merged your:
>    commit 1cca2bc0d7a9462bb1b59edb108bac7c9e7c424d
>    Author: Qu Wenruo <[email protected]>
>    Date:   Fri Jul 17 16:37:17 2026 +0930
> 
>        fstests: vfstest: skip rejected tmpfile creation
> 
> Since (Christian's) patch seems to replace yours (I think), so do you mind
> if I revert your patch and merge this one instead?

Yes, please. That's exactly what I expect.

Thanks,
Qu

> 
> Thanks,
> Zorro
> 
>>
>> Thanks,
>> Qu
>>
>>> ---
>>>    src/vfs/idmapped-mounts.c | 12 ++++++------
>>>    1 file changed, 6 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/src/vfs/idmapped-mounts.c b/src/vfs/idmapped-mounts.c
>>> index ed9992f9..8f8441c9 100644
>>> --- a/src/vfs/idmapped-mounts.c
>>> +++ b/src/vfs/idmapped-mounts.c
>>> @@ -3838,7 +3838,7 @@ int tcore_setgid_create_idmapped(const struct vfstest_info *info)
>>>    		goto out;
>>>    	}
>>> -	supported = openat_tmpfile_supported(open_tree_fd);
>>> +	supported = openat_tmpfile_supported(info->t_dir1_fd);
>>>    	pid = fork();
>>>    	if (pid < 0) {
>>> @@ -4014,7 +4014,7 @@ int tcore_setgid_create_idmapped_in_userns(const struct vfstest_info *info)
>>>    		goto out;
>>>    	}
>>> -	supported = openat_tmpfile_supported(open_tree_fd);
>>> +	supported = openat_tmpfile_supported(info->t_dir1_fd);
>>>    	pid = fork();
>>>    	if (pid < 0) {
>>> @@ -7733,7 +7733,7 @@ static int setgid_create_umask_idmapped(const struct vfstest_info *info)
>>>    		goto out;
>>>    	}
>>> -	supported = openat_tmpfile_supported(open_tree_fd);
>>> +	supported = openat_tmpfile_supported(info->t_dir1_fd);
>>>    	pid = fork();
>>>    	if (pid < 0) {
>>> @@ -7947,7 +7947,7 @@ static int setgid_create_umask_idmapped_in_userns(const struct vfstest_info *inf
>>>    		goto out;
>>>    	}
>>> -	supported = openat_tmpfile_supported(open_tree_fd);
>>> +	supported = openat_tmpfile_supported(info->t_dir1_fd);
>>>    	/*
>>>    	 * Below we verify that setgid inheritance for a newly created file or
>>> @@ -8181,7 +8181,7 @@ static int setgid_create_acl_idmapped(const struct vfstest_info *info)
>>>    		goto out;
>>>    	}
>>> -	supported = openat_tmpfile_supported(open_tree_fd);
>>> +	supported = openat_tmpfile_supported(info->t_dir1_fd);
>>>    	pid = fork();
>>>    	if (pid < 0) {
>>> @@ -8536,7 +8536,7 @@ static int setgid_create_acl_idmapped_in_userns(const struct vfstest_info *info)
>>>    		goto out;
>>>    	}
>>> -	supported = openat_tmpfile_supported(open_tree_fd);
>>> +	supported = openat_tmpfile_supported(info->t_dir1_fd);
>>>    	/*
>>>    	 * Below we verify that setgid inheritance for a newly created file or
>>>
>>