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From: Catalin Marinas <catalin.marinas@arm.com>
To: David Hildenbrand <david@redhat.com>
Cc: "Joey Gouly" <joey.gouly@arm.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Lennart Poettering" <lennart@poettering.net>,
	"Zbigniew Jędrzejewski-Szmek" <zbyszek@in.waw.pl>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Kees Cook" <keescook@chromium.org>,
	"Szabolcs Nagy" <szabolcs.nagy@arm.com>,
	"Mark Brown" <broonie@kernel.org>,
	"Jeremy Linton" <jeremy.linton@arm.com>,
	"Topi Miettinen" <toiwoton@gmail.com>,
	linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	linux-abi-devel@lists.sourceforge.net, nd@arm.com,
	shuah@kernel.org
Subject: Re: [PATCH v2 1/2] mm: Implement memory-deny-write-execute as a prctl
Date: Mon, 23 Jan 2023 16:22:11 +0000	[thread overview]
Message-ID: <Y860MziGHLafTjOU@arm.com> (raw)
In-Reply-To: <e07d958a-1400-3630-8a24-154850f41fb7@redhat.com>

On Mon, Jan 23, 2023 at 05:10:08PM +0100, David Hildenbrand wrote:
> On 23.01.23 17:04, Catalin Marinas wrote:
> > On Mon, Jan 23, 2023 at 01:53:46PM +0100, David Hildenbrand wrote:
> > > That at least would be then similar to how we handle mmaped files: if the
> > > file is not executable, we clear VM_MAYEXEC. If the file is not writable, we
> > > clear VM_MAYWRITE.
> > 
> > We still allow VM_MAYWRITE for private mappings, though we do clear
> > VM_MAYEXEC if not executable.
> > 
> > It would be nice to use VM_MAY* flags for this logic but we can only
> > emulate MDWE if we change the semantics of 'MAY': only check the 'MAY'
> > flags for permissions being changed (e.g. allow PROT_EXEC if the vma is
> > already VM_EXEC even if !VM_MAYEXEC). Another issue is that we end up
> > with some weird combinations like having VM_EXEC without VM_MAYEXEC
> > (maybe that's fine).
> 
> No, we wouldn't want VM_EXEC if VM_MAYEXEC is not set. I don't immediately
> see how that would happen.

You are right, this shouldn't happen. What I had in mind was the current
MDWE model where after an mmap(PROT_EXEC), any mprotect(PROT_EXEC) is
denied. But this series departs slightly from this since we want to
allow PROT_EXEC if already executable.

-- 
Catalin

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linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

WARNING: multiple messages have this Message-ID (diff)
From: Catalin Marinas <catalin.marinas@arm.com>
To: David Hildenbrand <david@redhat.com>
Cc: "Joey Gouly" <joey.gouly@arm.com>,
	"Andrew Morton" <akpm@linux-foundation.org>,
	"Lennart Poettering" <lennart@poettering.net>,
	"Zbigniew Jędrzejewski-Szmek" <zbyszek@in.waw.pl>,
	"Alexander Viro" <viro@zeniv.linux.org.uk>,
	"Kees Cook" <keescook@chromium.org>,
	"Szabolcs Nagy" <szabolcs.nagy@arm.com>,
	"Mark Brown" <broonie@kernel.org>,
	"Jeremy Linton" <jeremy.linton@arm.com>,
	"Topi Miettinen" <toiwoton@gmail.com>,
	linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	linux-abi-devel@lists.sourceforge.net, nd@arm.com,
	shuah@kernel.org
Subject: Re: [PATCH v2 1/2] mm: Implement memory-deny-write-execute as a prctl
Date: Mon, 23 Jan 2023 16:22:11 +0000	[thread overview]
Message-ID: <Y860MziGHLafTjOU@arm.com> (raw)
In-Reply-To: <e07d958a-1400-3630-8a24-154850f41fb7@redhat.com>

On Mon, Jan 23, 2023 at 05:10:08PM +0100, David Hildenbrand wrote:
> On 23.01.23 17:04, Catalin Marinas wrote:
> > On Mon, Jan 23, 2023 at 01:53:46PM +0100, David Hildenbrand wrote:
> > > That at least would be then similar to how we handle mmaped files: if the
> > > file is not executable, we clear VM_MAYEXEC. If the file is not writable, we
> > > clear VM_MAYWRITE.
> > 
> > We still allow VM_MAYWRITE for private mappings, though we do clear
> > VM_MAYEXEC if not executable.
> > 
> > It would be nice to use VM_MAY* flags for this logic but we can only
> > emulate MDWE if we change the semantics of 'MAY': only check the 'MAY'
> > flags for permissions being changed (e.g. allow PROT_EXEC if the vma is
> > already VM_EXEC even if !VM_MAYEXEC). Another issue is that we end up
> > with some weird combinations like having VM_EXEC without VM_MAYEXEC
> > (maybe that's fine).
> 
> No, we wouldn't want VM_EXEC if VM_MAYEXEC is not set. I don't immediately
> see how that would happen.

You are right, this shouldn't happen. What I had in mind was the current
MDWE model where after an mmap(PROT_EXEC), any mprotect(PROT_EXEC) is
denied. But this series departs slightly from this since we want to
allow PROT_EXEC if already executable.

-- 
Catalin


  reply	other threads:[~2023-01-23 16:35 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-01-19 16:03 [PATCH v2 0/2] mm: In-kernel support for memory-deny-write-execute (MDWE) Joey Gouly
2023-01-19 16:03 ` Joey Gouly
2023-01-19 16:03 ` [PATCH v2 1/2] mm: Implement memory-deny-write-execute as a prctl Joey Gouly
2023-01-19 16:03   ` Joey Gouly
2023-01-23 11:45   ` David Hildenbrand
2023-01-23 11:45     ` David Hildenbrand
2023-01-23 12:19     ` Catalin Marinas
2023-01-23 12:19       ` Catalin Marinas
2023-01-23 12:53       ` David Hildenbrand
2023-01-23 12:53         ` David Hildenbrand
2023-01-23 16:04         ` Catalin Marinas
2023-01-23 16:04           ` Catalin Marinas
2023-01-23 16:10           ` David Hildenbrand
2023-01-23 16:10             ` David Hildenbrand
2023-01-23 16:22             ` Catalin Marinas [this message]
2023-01-23 16:22               ` Catalin Marinas
2023-01-23 17:48           ` Topi Miettinen
2023-01-23 17:48             ` Topi Miettinen
2023-03-07 13:01   ` Alexey Izbyshev
2023-03-07 13:01     ` Alexey Izbyshev
2023-03-08 12:36     ` Catalin Marinas
2023-03-08 12:36       ` Catalin Marinas
2023-01-19 16:03 ` [PATCH v2 2/2] kselftest: vm: add tests for memory-deny-write-execute Joey Gouly
2023-01-19 16:03   ` Joey Gouly
2023-03-01 16:35   ` Peter Xu
2023-03-01 16:35     ` Peter Xu
2023-03-02 11:07     ` Joey Gouly
2023-03-02 11:07       ` Joey Gouly

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