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Re: [PATCH][v4][BZ #17523] linux: open and openat ignore 'mode' with O_TMPFILE in flags

From: Mike Frysinger <vapier at gentoo dot org>
To: Eric Rannaud <e at nanocritical dot com>
Cc: libc-alpha at sourceware dot org, Roland McGrath <roland at hack dot frob dot com>, joseph at codesourcery dot com, Florian Weimer <fweimer at redhat dot com>, Rich Felker <dalias at libc dot org>
Date: Tue, 17 Feb 2015 03:24:50 -0500
Subject: Re: [PATCH][v4][BZ #17523] linux: open and openat ignore 'mode' with O_TMPFILE in flags
Authentication-results: sourceware.org; auth=none
References: <98aff1222523cb913a73a52d36713fa50f738e41 dot 1418408433 dot git dot e at nanocritical dot com>

On 12 Dec 2014 10:32, Eric Rannaud wrote:
> Both open and openat load their last argument 'mode' lazily, using
> va_arg() only if O_CREAT is found in oflag. This is wrong, mode is also
> necessary if O_TMPFILE is in oflag.
> 
> By chance on x86_64, the problem wasn't evident when using O_TMPFILE
> with open, as the 3rd argument of open, even when not loaded with
> va_arg, is left untouched in RDX, where the syscall expects it.
> 
> However, openat was not so lucky, and O_TMPFILE couldn't be used: mode
> is the 4th argument, in RCX, but the syscall expects its 4th argument in
> a different register than the glibc wrapper, in R10.
> 
> Introduce a macro __OPEN_NEEDS_MODE (oflag) to test if either O_CREAT or
> O_TMPFILE is set in oflag.

lgtm.  since master is open again, guess should be easy to merge.
-mike

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