On 10/31/17 6:10 PM, Luis R. Rodriguez wrote:
> On Tue, Oct 31, 2017 at 03:43:20PM -0700, Darrick J. Wong wrote:
>> On Tue, Oct 31, 2017 at 03:19:00PM -0700, Luis R. Rodriguez wrote:
>>> On Tue, Oct 31, 2017 at 3:12 PM, Darrick J. Wong
>>> <darrick.wong@xxxxxxxxxx> wrote:
>>>> On Tue, Oct 31, 2017 at 02:51:56PM -0700, Luis R. Rodriguez wrote:
>>>>> diff --git a/repair/dinode.c b/repair/dinode.c
>>>>> index 15ba8cc22b39..6288e42de15e 100644
>>>>> --- a/repair/dinode.c
>>>>> +++ b/repair/dinode.c
>>>>> @@ -2482,6 +2482,27 @@ _("bad (negative) size %" PRId64 " on inode %" PRIu64 "\n"),
>>>>> FS_XFLAG_EXTSIZE);
>>>>> }
>>>>> }
>>>>> + if (flags & (XFS_DIFLAG_IMMUTABLE | XFS_DIFLAG_APPEND |
>>>>> + XFS_DIFLAG_NODUMP)) {
>>>>> + /*
>>>>> + * ioctl(fd, *) and so ioctl(fd, FS_IOC_SETFLAGS)
>>>>> + * yields EBADF on symlinks as they have O_PATH set.
>>>>> + * "Extra file attributes", stx_attributes, as per
>>>>> + * statx(2) cannot be set on symlinks on Linux.
>>>>> + */
>>>>> + if (di_mode && S_ISLNK(di_mode) &&
>>>>> + !S_ISREG(di_mode) && !S_ISDIR(di_mode)) {
>>>>
>>>> Does this DIFLAG clearing applies to bdev/cdev/fifo/socket files too?
>>>
>>> Not at the moment given the semantics I hunted down and tested for
>>> were for O_PATH only. The validation I hunted down applies to any
>>> file descriptors which we open via O_PATH only.
>>
>> iirc when you open one of those special files you end up with a fd that
>> points to an inode on a special bdevfs/pipefs/etc., not an inode linked
>> to the underlying filesystem containing the special file.
>
> That seems to fit the O_PATH intent, however its unclear if O_PATH was needed,
> as per my testing on /dev/loop0 I don't need O_PATH set for it.
>
>> Therefore you shouldn't be able to set any DIFLAG/DIFLAG2 flags on special files.
>
> That would be great if we can verify.
>
>> # mknod block b 8 0 ; mknod char c 1 3 ; mknod fifo p
>> # lsattr block char fifo
>> lsattr: Operation not supported While reading flags on block
>> lsattr: Operation not supported While reading flags on char
>> lsattr: Operation not supported While reading flags on fifo
>
> I'm afraid e2fsprogs has a special check for these, ie, userspace is barred
> from actually toying with special files purposely because of the Debian bug I
> named.
>
> strace should reveal the respective ioctl() was not actually issued.
That's very easy to short-circuit in e2fsprogs if you'd like to test what
the kernel does today.
-Eric
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