Re: [PATCHv10 man-pages 5/5] execveat.2: initial man page for execveat(2)

[Rich Felker]

On Fri, Jan 09, 2015 at 08:56:26PM +0000, Al Viro wrote:
> On Fri, Jan 09, 2015 at 03:48:15PM -0500, Rich Felker wrote:
> > I think this is a case that needs to be fixed, though it's hard. The
> > normal correct usage for fexecve is to always pass an O_CLOEXEC file
> > descriptor, and the caller can't really be expected to know whether
> > the file is a script or not. We discussed workarounds before and one
> > idea I proposed was having fexecve provide a "one open only" magic
> > symlink in /proc/self/ to pass to the interpreter. It would behave
> > like an O_PATH file descriptor magic symlink in /proc/self/fd, but
> > would automatically cease to exist on the first open (at which point
> > the interpreter would have a real O_RDONLY file descriptor for the
> > underlying file).
> 
> For fsck sake, folks, if you have bloody /proc, you don't need that shite
> at all!  Just do execve on /proc/self/fd/n, and be done with that.
> 
> The sole excuse for merging that thing in the first place had been
> "would anybody think of children^Wsclerotic^Whardened environments
> where they have no /proc at all".

That doesn't work. With O_CLOEXEC, /proc/self/fd/n is already gone at
the time the interpreter runs, whether you're using fexecveat or
execve with "/proc/self/fd/n" to implement POSIX fexecve(). That's the
problem. This breaks the intended idiom for fexecve.

Rich
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