Re: [PATCH 2/2] Ignore failure of setting mode on a temporary file on OS/2

On 10/17/23 11:16, Zack Weinberg wrote:
> On Sun, Oct 15, 2023, at 3:43 AM, KO Myung-Hun wrote:
>> How about this ?
>> 1. create and close a temporary file
>> 2. chmod() on it
>> 3. re-open it with O_TRUNC ?
> 
> The trouble is, on a multi-user system, any time you do any operation
> by name on a file whose full pathname includes a world-writable
> directory (such as the system-wide scratch directories), even if that
> directory is “sticky” (chmod +t), you have to be exquisitely careful,
> or a malicious concurrent process might be able to trick you into
> overwriting some file elsewhere on the filesystem.  For example, your
> steps 2 and 3, if executed as root on a file expected to exist in
> /tmp, would give a malicious concurrent process a chance to clobber
> the access control bits and/or the contents of *any file*, by moving
> the temporary file out of the way

? If /tmp is sticky, a malicious process can't rename /tmp/foo.

The rest of your email and patch look good to me, though admittedly I 
haven't used perl for real in 30 years.