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Date: Sat, 23 Feb 2013 00:21:01 -0500
From: KOSAKI Motohiro <kosaki.motohiro@...il.com>
To: Rich Felker <dalias@...ifal.cx>
Cc: libc-alpha <libc-alpha@...rceware.org>, musl@...ts.openwall.com
Subject: Re: O_EXEC and O_SEARCH
On Sat, Feb 23, 2013 at 12:05 AM, Rich Felker <dalias@...ifal.cx> wrote:
> On Sat, Feb 23, 2013 at 12:01:39AM -0500, KOSAKI Motohiro wrote:
>> > 1. Try to open with O_RDONLY. If it succeeds, we're done. This is
>> > REALLY nice because it means O_SEARCH and O_EXEC "just work" even on
>> > ancient or broken kernels as long as the target file is readable.
>>
>> Hmm..
>> This algorithm seems slightly strange to me. Why do you want to try O_RDONLY at
>> first?
>> O_RDONLY require read permission and O_SEARCH, if i understand correctly,
>> doesn't.
>> I think you should try O_PATH at first.
>
> If the file is readable, O_RDONLY will succeed and provides the
> necessary semantics for O_EXEC and O_SEARCH. The only time O_EXEC or
> O_SEARCH needs special support is when the file is not readable; these
> modes were specifically designed for supporting that case.
Ah, ok. got it.
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