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Re: [PATCH] xen/arm: call uaccess_ttbr0_enable for dm_op hypercall
- To: Stefano Stabellini <sstabellini@xxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- From: Jürgen Groß <jgross@xxxxxxxx>
- Date: Thu, 15 May 2025 13:33:19 +0200
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- Cc: Julien Grall <julien@xxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Michal Orzel <michal.orzel@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, stable@xxxxxxxxxx
- Delivery-date: Thu, 15 May 2025 11:33:38 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 12.05.25 23:54, Stefano Stabellini wrote:
From: Stefano Stabellini <stefano.stabellini@xxxxxxx>
dm_op hypercalls might come from userspace and pass memory addresses as
parameters. The memory addresses typically correspond to buffers
allocated in userspace to hold extra hypercall parameters.
On ARM, when CONFIG_ARM64_SW_TTBR0_PAN is enabled, they might not be
accessible by Xen, as a result ioreq hypercalls might fail. See the
existing comment in arch/arm64/xen/hypercall.S regarding privcmd_call
for reference.
For privcmd_call, Linux calls uaccess_ttbr0_enable before issuing the
hypercall thanks to commit 9cf09d68b89a. We need to do the same for
dm_op. This resolves the problem.
Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
Fixes: 9cf09d68b89a ("arm64: xen: Enable user access before a privcmd
hvc call")
Cc: stable@xxxxxxxxxx
I'm not an Arm specialist, but looking at the surrounding code this
seems to be correct.
Reviewed-by: Juergen Gross <jgross@xxxxxxxx>
Juergen
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