[Bug 42704] New: execve may return EAGAIN on v3.1 or later

[Bug 42704] New: execve may return EAGAIN on v3.1 or later

[bugzilla-daemon-590EEB7GvNiWaY/ihj7yzEB+6BGkLq7r]

https://bugzilla.kernel.org/show_bug.cgi?id=42704

           Summary: execve may return EAGAIN on v3.1 or later
           Product: Documentation
           Version: unspecified
          Platform: All
        OS/Version: Linux
              Tree: Mainline
            Status: NEW
          Severity: normal
          Priority: P1
         Component: man-pages
        AssignedTo: documentation_man-pages-ztI5WcYan/vQLgFONoPN62D2FQJk+8+b@public.gmane.org
        ReportedBy: kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org
        Regression: No


Following commit changed RLIMIT_NPROC rule. now set*uid() never return EAGAIN.
And instead,
execve() may return EAGAIN.

If man pages respect this change, it would be better.



commit 72fa59970f8698023045ab0713d66f3f4f96945c
Author: Vasiliy Kulikov 
Date:   Mon Aug 8 19:02:04 2011 +0400

    move RLIMIT_NPROC check from set_user() to do_execve_common()

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[Bug 42704] execve may return EAGAIN on v3.1 or later

[bugzilla-daemon-590EEB7GvNiWaY/ihj7yzEB+6BGkLq7r]

https://bugzilla.kernel.org/show_bug.cgi?id=42704


Michael Kerrisk <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org




--- Comment #1 from Michael Kerrisk <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>  2012-04-17 19:03:47 ---
Vasiliy,

Thanks for raising this bug. I think the best approach would be to leave the
existing EAGAIN text in the set*uid pages (possibly with a note about v3.1
changes), and add some text to the execve.2 page.

However, I have a question: I can understand adding the check to execve(), but
why was it removed from set*uid()? Surely it was still useful to applications
that actually do check the return status from set*uid()?

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[Bug 42704] execve may return EAGAIN on v3.1 or later

[bugzilla-daemon-590EEB7GvNiWaY/ihj7yzEB+6BGkLq7r]

https://bugzilla.kernel.org/show_bug.cgi?id=42704





--- Comment #2 from KOSAKI Motohiro <kosaki.motohiro-+CUm20s59erQFUHtdCDX3A@public.gmane.org>  2012-04-18 00:23:10 ---
Hmm..

I'm not Vasiliy and I couldn't add him to cc list (I don't know why).
But maybe I can answer this.

Now, many many applications don't check the return code and this ignorance may
make critical security issue. set*id() is usually used for dropping root
privilege 
 and then a failure mean application run untrusted code w/ root privilege.
that's dangerous. then, set*id() should ignore rlimit and always can drop a
privilege.

In the other hand, execve() is used for getting a privilege. then a failure is
not security threat.

Next, applications still should check set*uid() return value because it may run
on older kernel.

thank you.

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[Bug 42704] execve may return EAGAIN on v3.1 or later

[bugzilla-daemon-590EEB7GvNiWaY/ihj7yzEB+6BGkLq7r]

https://bugzilla.kernel.org/show_bug.cgi?id=42704

Michael Kerrisk <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|---                         |CODE_FIX

--- Comment #3 from Michael Kerrisk <mtk.manpages-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> ---
Patch (ebd381ba7b73) sitting in Git. Will be released with man-pages-3.69.

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