linux-kernel - Re: [PATCH] net: untag pointer in sockptr_is

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Message-ID: <20200811111551.GA3958@lst.de>
Date:   Tue, 11 Aug 2020 13:15:51 +0200
From:   Christoph Hellwig <hch@....de>
To:     Miles Chen <miles.chen@...iatek.com>
Cc:     Christoph Hellwig <hch@....de>,
        "David S . Miller" <davem@...emloft.net>,
        linux-kernel@...r.kernel.org, linux-mediatek@...ts.infradead.org,
        wsd_upstream@...iatek.com
Subject: Re: [PATCH] net: untag pointer in sockptr_is_kernel

On Tue, Aug 11, 2020 at 06:27:04PM +0800, Miles Chen wrote:
> From: Miles Chen <miles.chen@...iatek.com>
> 
> sockptr_is_kernel() uses (sockptr.kernel >= TASK_SIZE) to tell
> if the pointer is kernel space or user space. When user space uses
> the "top byte ignored" feature such as HWAsan, we must untag
> the pointer before checking against TASK_SIZE.
> 
> sockptr_is_kernel() will view a tagged user pointer as a kernel pointer
> and use memcpy directly and causes a kernel crash.

Dave merged a patch from me to rever the optimized sockptr
implementation for now.  If we bring it back we should fold in your
fix.