Re: [patch 12/12] vfs: allow file truncations when both suid and write permissions set

[OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>]

Amerigo Wang <amwang@redhat.com> writes:

> OGAWA Hirofumi wrote:
>> I found the SuSv3 says for ftruncate():
>>
>> Upon successful completion, if fildes refers to a regular file,
>> ftruncate() shall mark for update the last data modification and last
>> file status change timestamps of the file and the S_ISUID and S_ISGID
>> bits of the file mode may be cleared. If the ftruncate() function is
>> unsuccessful, the file is unaffected.
>>
>> And vmtruncate() can return error easily with RLIMIT_FSIZE or
>> ->s_maxbytes. So, I think clearing s[ug]id first may be bad behavior
>> without good reason.
>>   
>
> Hmm, you mean we should clear suid after we do notify_change()?
> Good point!

I guess it would be better than current patch in practice, although it's
not perfect.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>