Date: Tue, 4 Jul 2017 16:48:17 +0200
From: Michal Hocko <mhocko@kernel.org>
To: Ximin Luo <infinity0@debian.org>
Cc: Ben Hutchings <ben@decadent.org.uk>, Willy Tarreau <w@1wt.eu>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Hugh Dickins <hughd@google.com>, Oleg Nesterov <oleg@redhat.com>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>, Rik van Riel <riel@redhat.com>,
        Larry Woodman <lwoodman@redhat.com>,
        "Kirill A. Shutemov" <kirill@shutemov.name>,
        Tony Luck <tony.luck@intel.com>,
        "James E.J. Bottomley" <jejb@parisc-linux.org>,
        Helge Diller <deller@gmx.de>, James Hogan <james.hogan@imgtec.com>,
        Laura Abbott <labbott@redhat.com>, Greg KH <greg@kroah.com>,
        "security@kernel.org" <security@kernel.org>,
        linux-distros@vs.openwall.org,
        Qualys Security Advisory <qsa@qualys.com>,
        LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] mm: larger stack guard gap, between vmas
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On Tue 04-07-17 14:19:00, Ximin Luo wrote:
[...]
> I've written up an explanation of what happens in the Rust case here:
> 
> https://github.com/rust-lang/rust/issues/43052

The most important part is https://github.com/rust-lang/rust/blob/master/src/libstd/sys/unix/thread.rs#L248
        // Rellocate the last page of the stack.
        // This ensures SIGBUS will be raised on
        // stack overflow.
        let result = mmap(stackaddr, psize, PROT_NONE, MAP_PRIVATE | MAP_ANON | MAP_FIXED, -1, 0);

so this is basically the same thing Java does. Except that Java doesn't
do that on main thread usually. Only some JNI runtimes do that.
pthread_attr_getstack() usage on the main thread sounds like a real bug
in rust to me.

Thanks for the writeup!
-- 
Michal Hocko
SUSE Labs