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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