From: Thomas Huth <1875702@bugs.launchpad.net>
To: qemu-devel@nongnu.org
Subject: [Bug 1875702] Re: madvise reports success, but doesn't implement WIPEONFORK.
Date: Thu, 06 May 2021 13:33:29 -0000 [thread overview]
Message-ID: <162030800998.6598.8113594581143069191.malone@wampee.canonical.com> (raw)
In-Reply-To: 158809456539.8338.16342287412940632416.malonedeb@chaenomeles.canonical.com
The QEMU project is currently moving its bug tracking to another system.
For this we need to know which bugs are still valid and which could be
closed already. Thus we are setting older bugs to "Incomplete" now.
If you still think this bug report here is valid, then please switch
the state back to "New" within the next 60 days, otherwise this report
will be marked as "Expired". Or please mark it as "Fix Released" if
the problem has been solved with a newer version of QEMU already.
Thank you and sorry for the inconvenience.
** Changed in: qemu
Status: New => Incomplete
** Tags added: linux-user
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https://bugs.launchpad.net/bugs/1875702
Title:
madvise reports success, but doesn't implement WIPEONFORK.
Status in QEMU:
Incomplete
Bug description:
The implementation of madvise (linux-user/syscall.c:11331, tag
v5.0.0-rc4) always returns zero (i.e. success). However, an
application requesting (at least) MADV_WIPEONFORK may need to know
whether the call was actually successful. If not (because the kernel
doesn't support WIPEONFORK) then it will need to take other measures
to provide fork-safety (such as drawing entropy from the kernel in
every case). But, if the application believes that WIPEONFORK is
supported (because madvise returned zero), but it actually isn't (as
in qemu), then it may forego those protections on the assumption that
WIPEONFORK will provide fork-safety.
Roughly, the comment in qemu that says "This is a hint, so ignoring
and returning success is ok." is no longer accurate in the presence of
MADV_WIPEONFORK.
(This is not purely academic: BoringSSL is planning on acting in this
way. We found the qemu behaviour in pre-release testing and are
planning on making an madvise call with advice=-1 first to test
whether unknown advice values actually produce EINVAL.)
To manage notifications about this bug go to:
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next prev parent reply other threads:[~2021-05-06 13:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-28 17:22 [Bug 1875702] [NEW] madvise reports success, but doesn't implement WIPEONFORK agl
2020-04-30 14:04 ` [Bug 1875702] " Laurent Vivier
2021-05-06 13:33 ` Thomas Huth [this message]
2021-05-06 13:50 ` Peter Maydell
2021-05-18 23:45 ` Thomas Huth
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