From: Andrew Morton <akpm@linux-foundation.org>
To: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>,
linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
Szabolcs Nagy <szabolcs.nagy@arm.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Florian Weimer <fweimer@redhat.com>,
Victor Stinner <vstinner@redhat.com>,
Andrey Konovalov <andreyknvl@google.com>
Subject: Re: [PATCH v2] mm: Avoid creating virtual address aliases in brk()/mmap()/mremap()
Date: Wed, 19 Feb 2020 11:40:20 -0800 [thread overview]
Message-ID: <20200219114020.0d6c730abce1cdd77e4e5487@linux-foundation.org> (raw)
In-Reply-To: <20200219134602.GB21366@willie-the-truck>
On Wed, 19 Feb 2020 13:46:03 +0000 Will Deacon <will@kernel.org> wrote:
> On Wed, Feb 19, 2020 at 12:31:56PM +0000, Catalin Marinas wrote:
> > Currently the arm64 kernel ignores the top address byte passed to brk(),
> > mmap() and mremap(). When the user is not aware of the 56-bit address
> > limit or relies on the kernel to return an error, untagging such
> > pointers has the potential to create address aliases in user-space.
> > Passing a tagged address to munmap(), madvise() is permitted since the
> > tagged pointer is expected to be inside an existing mapping.
> >
> > The current behaviour breaks the existing glibc malloc() implementation
> > which relies on brk() with an address beyond 56-bit to be rejected by
> > the kernel.
> >
> > Remove untagging in the above functions by partially reverting commit
> > ce18d171cb73 ("mm: untag user pointers in mmap/munmap/mremap/brk"). In
> > addition, update the arm64 tagged-address-abi.rst document accordingly.
> >
> > Link: https://bugzilla.redhat.com/1797052
> > Fixes: ce18d171cb73 ("mm: untag user pointers in mmap/munmap/mremap/brk")
> > Cc: <stable@vger.kernel.org> # 5.4.x-
> > Cc: Andrew Morton <akpm@linux-foundation.org>
> > Cc: Florian Weimer <fweimer@redhat.com>
> > Reported-by: Victor Stinner <vstinner@redhat.com>
> > Acked-by: Will Deacon <will@kernel.org>
> > Acked-by: Andrey Konovalov <andreyknvl@google.com>
> > Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
> > ---
> >
> > Changes in v2:
> >
> > - Added note to tagged-address-abi.rst that this behaviour changed in v5.6 and
> > some older kernel may still have the old behaviour.
> >
> > - Updated the commit log to make it clearer we broke the user ABI, also adding
> > link to the Red Hat bugzilla entry.
>
> Cheers, I'll queue this up as I have a couple of other arm64 fixes pending
> now. (Andrew, please shout if you'd prefer to take it).
Please go ahead.
Reviewed-by: Andrew Morton <akpm@linux-foundation.org>
prev parent reply other threads:[~2020-02-19 19:40 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-19 12:31 [PATCH v2] mm: Avoid creating virtual address aliases in brk()/mmap()/mremap() Catalin Marinas
2020-02-19 13:46 ` Will Deacon
2020-02-19 19:40 ` Andrew Morton [this message]
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