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Message-ID: <20110822100512.GA2878@albatros>
Date: Mon, 22 Aug 2011 14:05:12 +0400
From: Vasiliy Kulikov <segoon@...nwall.com>
To: kernel-hardening@...ts.openwall.com
Subject: Re: kmalloc() nofail allocations
Solar,
On Mon, Aug 22, 2011 at 13:53 +0400, Solar Designer wrote:
> However, is there any difference for the caller between kmalloc()
> looping until success (and thus only returning on success) and it
> OOM-killing the current process (and thus also only returning on
> success)? Or does this question somehow not apply to the problem you
> discovered?
The "cannot fail" loop stops if the current task is marked as
to-be-killed-by-oom-killer. OOM killer doesn't immediately kill the
task, the task exits itself after the exit from kernel mode and a
scheduler step (AFAIU).
So, AFAICS, the loop is executed only if:
1) Appropriate flags are passed (no NOWAIT, etc.), sane NUMA node list is
passed (e.g. not GFP_THISNODE and node list without current node).
2) Size is not big (less than PAGE_SIZE << 3).
3) Debugging allocation failure injection is either off or has a
min size more than the current allocation size.
4) OOM killer didn't mark the task with TIF_MEMDIE.
Thanks,
--
Vasiliy
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