Re: [PATCH] fanotify: add a flag to allow setting O_CLOEXEC on event fd

From: Michael Kerrisk (man-pages)
Date: Thu Oct 02 2014 - 07:56:19 EST


On Thu, Oct 2, 2014 at 11:13 AM, PÃdraig Brady <P@xxxxxxxxxxxxxx> wrote:
> On 10/02/2014 08:52 AM, Yann Droneaud wrote:
>> In order to not potentially break applications which were
>> requesting O_CLOEXEC on event file descriptors but which
>> actually need it to be not effective as the kernel currently
>> ignore the flag, so the file descriptor is inherited accross
>> exec regardless of O_CLOEXEC (please forgive me for the
>> wording), this patch introduces FAN_FD_CLOEXEC flag to
>> fanotify_init() so that application can request O_CLOEXEC
>> to be effective.
>> Newer application would use FAN_FD_CLOEXEC flag along
>> O_CLOEXEC to enable close on exec on newly created
>> file descriptor:
>>
>> fd = fanotify_init(FAN_CLOEXEC|FAN_NONBLOCK|FAN_FD_CLOEXEC,
>> O_RDONLY|O_LARGEFILE|O_CLOEXEC|O_NOATIME);
>
> Ugh really?
> IMHO there should be widespread or at least known breakage with
> O_CLOEXEC before adding messiness like this.
> It seems surprising to me that apps that would depend on
> O_CLOEXEC being ineffective.
>
> please reconsider this one.

Agreed. The number of applications for which there are silent (not
*yet* observed) breakages because O_CLOEXEC is not working as expected
is likely rather larger than the set of applications that randomly
specify O_CLOEXEC and then somehow get broken as a result.

Cheers,

Michael


--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/