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Re: [PATCH] optee: immediately free RPC buffers that are released by OP-TEE
- To: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
- From: Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
- Date: Wed, 4 May 2022 19:59:22 +0000
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- Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>
- Delivery-date: Wed, 04 May 2022 19:59:48 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
- Thread-index: AQHYX3q1+cwfT5uujESolgz3RZy+760PI7EA
- Thread-topic: [PATCH] optee: immediately free RPC buffers that are released by OP-TEE
Hello Jens,
Jens Wiklander <jens.wiklander@xxxxxxxxxx> writes:
> This commit fixes a case overlooked in [1].
>
> There are two kinds of shared memory buffers used by OP-TEE:
> 1. Normal payload buffer
> 2. Internal command structure buffers
>
> The internal command structure buffers are represented with a shadow
> copy internally in Xen since this buffer can contain physical addresses
> that may need to be translated between real physical address and guest
> physical address without leaking information to the guest.
>
> [1] fixes the problem when releasing the normal payload buffers. The
> internal command structure buffers must be released in the same way.
> Failure to follow this order opens a window where the guest has freed
> the shared memory but Xen is still tracking the buffer.
>
> During this window the guest may happen to recycle this particular
> shared memory in some other thread and try to use it. Xen will block
> this which will lead to spurious failures to register a new shared
> memory block.
>
> Fix this by freeing the internal command structure buffers first before
> informing the guest that the buffer can be freed.
>
> [1] 5b13eb1d978e ("optee: immediately free buffers that are released by
> OP-TEE")
>
> Signed-off-by: Jens Wiklander <jens.wiklander@xxxxxxxxxx>
Thank you for the fix:
Reviewed-by: Volodymyr Babchuk <volodymyr_babchuk@xxxxxxxx>
--
Volodymyr Babchuk at EPAM
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