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Message-ID: <76da1bcd-0d00-4701-8f6f-cc28b5184bce@zytor.com>
Date:   Wed, 15 Nov 2023 20:31:20 -0800
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Subject: Re: [PATCH] x86: Fix 32-bit compatible userspace write size overflow
 error
To:     Jinjie Ruan <ruanjinjie@huawei.com>, linux-kernel@vger.kernel.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org
References: <20231115105626.953273-1-ruanjinjie@huawei.com>
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From:   "H. Peter Anvin" <hpa@zytor.com>
In-Reply-To: <20231115105626.953273-1-ruanjinjie@huawei.com>
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It's not clear to me that this is actually the correct behavior; the 
important thing is that it faults (as nothing is mapped above 4 GB anyway.)

	-hpa


On 11/15/23 02:56, Jinjie Ruan wrote:
> For 32-bit compatible userspace program, write with size = -1 return not
> -1 but unexpected other values, which is due to the __access_ok() check is
> insufficient. The specified "ptr + size" is greater than 32-bit limit and
> should return -EFAULT, but it is not checked and can not catch the overflow
> error.
> 
> Fix above error by checking 32-bit limit if it is 32-bit compatible
> userspace program.

	-hpa