Thread (41 messages) 41 messages, 8 authors, 2015-01-12

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

From: Al Viro <hidden>
Date: 2015-01-09 21:09:48
Also in: linux-arch, lkml, sparclinux

On Fri, Jan 09, 2015 at 03:59:26PM -0500, Rich Felker wrote:
quoted
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.
Just what will your magical symlink do in case when the file is opened,
unlinked and marked O_CLOEXEC?  When should actual freeing of disk blocks,
etc. happen?  And no, you can't assume that interpreter will open the
damn thing even once - there's nothing to oblige it to do so.

Al, more and more tempted to ask reverting the whole thing - this hardcoded
/dev/fd/... (in fs/exec.c, no less) is disgraceful enough, but threats of
even more revolting kludges in the name of "intended idiom for fexecve"...
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