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Message-ID: <20130223050542.GX20323@brightrain.aerifal.cx>
Date: Sat, 23 Feb 2013 00:05:42 -0500
From: Rich Felker <dalias@...ifal.cx>
To: KOSAKI Motohiro <kosaki.motohiro@...il.com>
Cc: libc-alpha <libc-alpha@...rceware.org>, musl@...ts.openwall.com
Subject: Re: O_EXEC and O_SEARCH
On Sat, Feb 23, 2013 at 12:01:39AM -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.
Rich
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