> On May 3, 2023, at 7:05 AM, Chuck Lever III <chuck.lever@xxxxxxxxxx> wrote:
>
>
>
>> On May 3, 2023, at 6:53 AM, Harshit Mogalapalli <harshit.m.mogalapalli@xxxxxxxxxx> wrote:
>>
>> Hi Christian,
>>
>> On 03/05/23 12:30 pm, Christian Brauner wrote:
>>> On Tue, May 02, 2023 at 06:23:51PM +0000, Chuck Lever III wrote:
>>>>
>>>>
>>>>> On May 2, 2023, at 12:50 PM, Chuck Lever III <chuck.lever@xxxxxxxxxx> wrote:
>>>>>
>>>>>
>>>>>
>>>>>> On May 2, 2023, at 9:49 AM, Chuck Lever III <chuck.lever@xxxxxxxxxx> wrote:
>>>>>>
>>>>>>>
>>>>>>> On May 2, 2023, at 9:36 AM, Christian Brauner <brauner@xxxxxxxxxx> wrote:
>>>>>>>
>>>>>>> We've aligned setgid behavior over multiple kernel releases. The details
>>>>>>> can be found in commit cf619f891971 ("Merge tag 'fs.ovl.setgid.v6.2' of
>>>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/vfs/idmapping") and
>>>>>>> commit 426b4ca2d6a5 ("Merge tag 'fs.setgid.v6.0' of
>>>>>>> git://git.kernel.org/pub/scm/linux/kernel/git/brauner/linux").
>>>>>>> Consistent setgid stripping behavior is now encapsulated in the
>>>>>>> setattr_should_drop_sgid() helper which is used by all filesystems that
>>>>>>> strip setgid bits outside of vfs proper. Usually ATTR_KILL_SGID is
>>>>>>> raised in e.g., chown_common() and is subject to the
>>>>>>> setattr_should_drop_sgid() check to determine whether the setgid bit can
>>>>>>> be retained. Since nfsd is raising ATTR_KILL_SGID unconditionally it
>>>>>>> will cause notify_change() to strip it even if the caller had the
>>>>>>> necessary privileges to retain it. Ensure that nfsd only raises
>>>>>>> ATR_KILL_SGID if the caller lacks the necessary privileges to retain the
>>>>>>> setgid bit.
>>>>>>>
>>>>>>> Without this patch the setgid stripping tests in LTP will fail:
>>>>>>>
>>>>>>>> As you can see, the problem is S_ISGID (0002000) was dropped on a
>>>>>>>> non-group-executable file while chown was invoked by super-user, while
>>>>>>>
>>>>>>> [...]
>>>>>>>
>>>>>>>> fchown02.c:66: TFAIL: testfile2: wrong mode permissions 0100700, expected 0102700
>>>>>>>
>>>>>>> [...]
>>>>>>>
>>>>>>>> chown02.c:57: TFAIL: testfile2: wrong mode permissions 0100700, expected 0102700
>>>>>>>
>>>>>>> With this patch all tests pass.
>>>>>>>
>>>>>>> Reported-by: Sherry Yang <sherry.yang@xxxxxxxxxx>
>>>>>>> Signed-off-by: Christian Brauner <brauner@xxxxxxxxxx>
>>>>>>
>>
>> We had a very similar report from kernel-test-robot.
>>
>> https://lore.kernel.org/all/202210091600.dbe52cbf-yujie.liu@xxxxxxxxx/
>>
>> Which points to commit: ed5a7047d201 ("attr: use consistent sgid stripping checks")
>>
>> And the above commit is backported to LTS kernels -- 5.10.y,5.15.y and 6.1.y
>>
>> So would it be better to tag it to stable by adding "Cc: <stable@xxxxxxxxxxxxxxx>" ?
>>
>> Thanks,
>> Harshit
>>
>>>>>> There are some similar fstests failures this fix might address.
>>>>>>
>>>>>> I've applied this patch to the nfsd-fixes tree for broader
>>>>>> testing.
>>>>>
>>>>> ERROR: modpost: "setattr_should_drop_sgid" [fs/nfsd/nfsd.ko] undefined!
>>>>>
>>>>> Did I apply this patch to the wrong kernel?
>>>>
>>>> setattr_should_drop_sgid() is not available to callers built as
>>>> modules. It needs an EXPORT_SYMBOL or _GPL.
>>> Hey Chuck,
>>> Thanks for taking a look!
>>> The required export is part of
>>> commit 4f704d9a835 ("nfs: use vfs setgid helper")
>>> which is in current mainline as of Monday this week which was part of my
>>> v6.4/vfs.misc PR that was merged.
>>> So this should all work fine on mainline. Seems I didn't use --base
>>> which is why that info was missing.
>>> Thanks!
>>> Christian
>
> I'll apply this to nfsd-next (6.5) and add Jeff's Reviewed-by
> and a Cc: stable.
Hi Chuck,
Just following up to see if you know when this patch will go to linux mainline and linux-stable?
Thanks,
Sherry
>
>
> --
> Chuck Lever
>
>
