* [Bug libc/10354] posix_spawn should use vfork() in more cases than presently
[not found] <bug-10354-131@http.sourceware.org/bugzilla/>
@ 2011-10-10 3:09 ` bugdal at aerifal dot cx
2011-10-15 13:47 ` drepper.fsp at gmail dot com
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From: bugdal at aerifal dot cx @ 2011-10-10 3:09 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=10354
Rich Felker <bugdal at aerifal dot cx> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
CC| |bugdal at aerifal dot cx
Resolution|WONTFIX |
--- Comment #2 from Rich Felker <bugdal at aerifal dot cx> 2011-10-10 03:08:20 UTC ---
The excuse for not fixing this does not make sense. The syscalls could be used
directly (without the wrapper code for cancellation), or cancellation could
simply be disabled by the parent prior to vfork and reenabled by the parent
after vfork returns (which won't happen until the child calls exec).
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[not found] <bug-10354-131@http.sourceware.org/bugzilla/>
2011-10-10 3:09 ` bugdal at aerifal dot cx
@ 2011-10-15 13:47 ` drepper.fsp at gmail dot com
2011-10-15 20:53 ` bugdal at aerifal dot cx
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From: drepper.fsp at gmail dot com @ 2011-10-15 13:47 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=10354
Ulrich Drepper <drepper.fsp at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|REOPENED |RESOLVED
Resolution| |FIXED
--- Comment #3 from Ulrich Drepper <drepper.fsp at gmail dot com> 2011-10-15 13:47:29 UTC ---
(In reply to comment #2)
> The excuse for not fixing this does not make sense.
What doesn't make sense is you. The function is defined in terms of using
close, open etc. The semantics is fixed.
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[not found] <bug-10354-131@http.sourceware.org/bugzilla/>
2011-10-10 3:09 ` bugdal at aerifal dot cx
2011-10-15 13:47 ` drepper.fsp at gmail dot com
@ 2011-10-15 20:53 ` bugdal at aerifal dot cx
2012-10-21 17:00 ` bugdal at aerifal dot cx
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From: bugdal at aerifal dot cx @ 2011-10-15 20:53 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=10354
--- Comment #4 from Rich Felker <bugdal at aerifal dot cx> 2011-10-15 20:52:20 UTC ---
It's defined in terms of open, close, etc. happening in the context of the
child process, where cancellation cannot play any role since there's no way to
obtain a pthread_t value referring to a thread in the child. Of course
implementing posix_spawn using vfork causes the cancellation state to be shared
with the parent, which would be problematic unless special care is made to
protect the state. I suggested several ways this could be done to allow vfork
to be used for posix_spawn in all cases.
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[not found] <bug-10354-131@http.sourceware.org/bugzilla/>
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2011-10-15 20:53 ` bugdal at aerifal dot cx
@ 2012-10-21 17:00 ` bugdal at aerifal dot cx
2014-02-10 21:21 ` sionescu+BugTrackers at cddr dot org
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From: bugdal at aerifal dot cx @ 2012-10-21 17:00 UTC (permalink / raw)
To: glibc-bugs
http://sourceware.org/bugzilla/show_bug.cgi?id=10354
Rich Felker <bugdal at aerifal dot cx> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |REOPENED
Resolution|FIXED |
--- Comment #5 from Rich Felker <bugdal at aerifal dot cx> 2012-10-21 16:59:58 UTC ---
This bug was marked "fixed" for no apparent reason. The issues reported still
exist; vfork is not used if any non-default attributes or file actions are
present. This makes it impossible to use posix_spawn from extremely large
processes due to commit charge exhaustion.
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2012-10-21 17:00 ` bugdal at aerifal dot cx
@ 2014-02-10 21:21 ` sionescu+BugTrackers at cddr dot org
2014-02-16 17:45 ` jackie.rosen at hushmail dot com
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From: sionescu+BugTrackers at cddr dot org @ 2014-02-10 21:21 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=10354
Stelian Ionescu <sionescu+BugTrackers at cddr dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |sionescu+BugTrackers at cddr dot o
| |rg
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2014-02-10 21:21 ` sionescu+BugTrackers at cddr dot org
@ 2014-02-16 17:45 ` jackie.rosen at hushmail dot com
2014-05-27 22:36 ` P at draigBrady dot com
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From: jackie.rosen at hushmail dot com @ 2014-02-16 17:45 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=10354
Jackie Rosen <jackie.rosen at hushmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |jackie.rosen at hushmail dot com
--- Comment #6 from Jackie Rosen <jackie.rosen at hushmail dot com> ---
*** Bug 260998 has been marked as a duplicate of this bug. ***
Seen from the domain http://volichat.com
Page where seen: http://volichat.com/adult-chat-rooms
Marked for reference. Resolved as fixed @bugzilla.
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2014-02-16 17:45 ` jackie.rosen at hushmail dot com
@ 2014-05-27 22:36 ` P at draigBrady dot com
2014-05-28 19:47 ` schwab at sourceware dot org
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From: P at draigBrady dot com @ 2014-05-27 22:36 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=10354
Pádraig Brady <P at draigBrady dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |P at draigBrady dot com
--- Comment #7 from Pádraig Brady <P at draigBrady dot com> ---
It's important that posix_spawn() avoids fork() where possible as that's the
whole reason for having this interface. I see that one can force using
vfork() with the POSIX_SPAWN_USEVFORK flag as mentioned in bug #378
though then you're on your own wrt safety.
So I'm wondering what specifically callers of posix_spawn() would
have to be careful to do?
* Not setup pthread_atfork() handlers
* pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, NULL); first (and enable
after)
* anything else?
Also I was wondering whether some restrictions could be lifted in
the implementation by using clone() rather than vfork().
I.E. vfork() where possible to support MMU less systems,
but then fall back to clone(..., CLONE_VM | SIGCHLD, ...);
to at least have an otherwise efficient implementation.
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Subject: [Bug libc/10354] posix_spawn should use vfork() in more cases than presently
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https://sourceware.org/bugzilla/show_bug.cgi?id\x10354
--- Comment #8 from Rich Felker <bugdal at aerifal dot cx> ---
Using clone with CLONE_VM and a new stack/start-function solves most of the
insurmountable problems with vfork that make it unsafe, but there are still a
number of considerations that come from sharing memory. In particular, you must
ensure that no signal handlers run in the child while it's sharing memory with
the parent, and the parent must be responsible for freeing the child's stack,
and thus must synchronize with the execve call in the child.
I have a working implementation in musl which solves these problems (it uses
clone with CLONE_VM for all posix_spawn operations) if anyone is interested in
looking at it and doing something similar for glibc.
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@ 2014-05-28 19:47 ` schwab at sourceware dot org
2014-05-28 19:47 ` schwab at sourceware dot org
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From: schwab at sourceware dot org @ 2014-05-28 19:47 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=10354
Andreas Schwab <schwab at sourceware dot org> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC|jackie.rosen at hushmail dot com |
|jackie.rosen at hushmail dot com |
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2014-05-28 19:47 ` schwab at sourceware dot org
@ 2014-05-28 19:47 ` schwab at sourceware dot org
2014-07-01 7:53 ` fweimer at redhat dot com
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From: schwab at sourceware dot org @ 2014-05-28 19:47 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=10354
Andreas Schwab <schwab at sourceware dot org> changed:
What |Removed |Added
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CC|jackie.rosen at hushmail dot com |
|jackie.rosen at hushmail dot com |
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2014-05-28 19:47 ` schwab at sourceware dot org
@ 2014-07-01 7:53 ` fweimer at redhat dot com
2014-09-20 4:22 ` carlos at redhat dot com
2023-06-16 0:35 ` sam at gentoo dot org
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From: fweimer at redhat dot com @ 2014-07-01 7:53 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=10354
Florian Weimer <fweimer at redhat dot com> changed:
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CC| |fweimer at redhat dot com
Flags| |security-
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2014-07-01 7:53 ` fweimer at redhat dot com
@ 2014-09-20 4:22 ` carlos at redhat dot com
2023-06-16 0:35 ` sam at gentoo dot org
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From: carlos at redhat dot com @ 2014-09-20 4:22 UTC (permalink / raw)
To: glibc-bugs
https://sourceware.org/bugzilla/show_bug.cgi?id=10354
Carlos O'Donell <carlos at redhat dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |carlos at redhat dot com
--- Comment #9 from Carlos O'Donell <carlos at redhat dot com> ---
(In reply to Rich Felker from comment #8)
> Using clone with CLONE_VM and a new stack/start-function solves most of the
> insurmountable problems with vfork that make it unsafe, but there are still
> a number of considerations that come from sharing memory. In particular, you
> must ensure that no signal handlers run in the child while it's sharing
> memory with the parent, and the parent must be responsible for freeing the
> child's stack, and thus must synchronize with the execve call in the child.
>
> I have a working implementation in musl which solves these problems (it uses
> clone with CLONE_VM for all posix_spawn operations) if anyone is interested
> in looking at it and doing something similar for glibc.
I agree this issue should be fixed.
posix_spawn() could use vfork() in many more cases than it does today, and
cancellation is no excuse not to fix this. I agree that cancellation in the
context of the child doesn't make any sense. The child needs to just not touch
the cancel state, and with signals blocked it will never act on a SIGCANCEL
request anyway.
We can perhaps revisit this after we fix cancellation to work correctly.
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2014-09-20 4:22 ` carlos at redhat dot com
@ 2023-06-16 0:35 ` sam at gentoo dot org
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From: sam at gentoo dot org @ 2023-06-16 0:35 UTC (permalink / raw)
To: glibc-bugs
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Sam James <sam at gentoo dot org> changed:
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CC| |sam at gentoo dot org
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