linux-kernel - mprotect outbound check.

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Date:   Mon, 15 May 2023 11:00:27 -0700
From:   Jeff Xu <jeffxu@...omium.org>
To:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        akpm@...ux-foundation.org, linux-hardening@...r.kernel.org,
        Jorge Lucangeli Obes <jorgelo@...omium.org>
Subject: mprotect outbound check.

Noticed there is a slight change for mprotect between 6.1 and 6.4 RC1

For example:
Consider the case below:
1 mmap(0x5000000, PAGE_SIZE,  ...)
2 mprotect(0x5000000, PAGE_SIZE*4, ...)

in 6.1 and before, 2 will fail, and in 6.4 RC1, it will pass.

I know that munmap will accept out-of-bound cases like this (because
memory is freed anyway).

Is this change intentional ?

Thanks!
Best regards,
-Jeff