linux-kernel - Re: [PATCH v2] arm64: pageattr: Explicitly bail out when changing permissions for vmalloc

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Message-Id: <174594039520.474971.2876521667626295214.b4-ty@kernel.org>
Date: Tue, 29 Apr 2025 21:27:45 +0100
From: Will Deacon <will@...nel.org>
To: catalin.marinas@....com,
	Dev Jain <dev.jain@....com>
Cc: kernel-team@...roid.com,
	Will Deacon <will@...nel.org>,
	gshan@...hat.com,
	rppt@...nel.org,
	steven.price@....com,
	suzuki.poulose@....com,
	tianyaxiong@...inos.cn,
	ardb@...nel.org,
	david@...hat.com,
	ryan.roberts@....com,
	urezki@...il.com,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] arm64: pageattr: Explicitly bail out when changing permissions for vmalloc_huge mappings

On Thu, 03 Apr 2025 10:58:44 +0530, Dev Jain wrote:
> arm64 uses apply_to_page_range to change permissions for kernel vmalloc mappings,
> which does not support changing permissions for block mappings. This function
> will change permissions until it encounters a block mapping, and will bail
> out with a warning. Since there are no reports of this triggering, it
> implies that there are currently no cases of code doing a vmalloc_huge()
> followed by partial permission change. But this is a footgun waiting to
> go off, so let's detect it early and avoid the possibility of permissions
> in an intermediate state. So,  explicitly disallow changing permissions
> for VM_ALLOW_HUGE_VMAP mappings.
> 
> [...]

Applied to arm64 (for-next/mm), thanks!

[1/1] arm64: pageattr: Explicitly bail out when changing permissions for vmalloc_huge mappings
      https://git.kernel.org/arm64/c/fcf8dda8cc48

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev