linux-kernel - Re: [PATCH] mm/mremap: Add comment explaining the untagging behaviour of mremap()

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Message-ID: <20200325112309.GM3901@mbp>
Date:   Wed, 25 Mar 2020 11:23:10 +0000
From:   Catalin Marinas <catalin.marinas@....com>
To:     Will Deacon <will@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kernel-team@...roid.com,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] mm/mremap: Add comment explaining the untagging
 behaviour of mremap()

On Wed, Mar 25, 2020 at 11:13:46AM +0000, Will Deacon wrote:
> Commit dcde237319e6 ("mm: Avoid creating virtual address aliases in
> brk()/mmap()/mremap()") changed mremap() so that only the 'old' address
> is untagged, leaving the 'new' address in the form it was passed from
> userspace. This prevents the unexpected creation of aliasing virtual
> mappings in userspace, but looks a bit odd when you read the code.
> 
> Add a comment justifying the untagging behaviour in mremap().
> 
> Cc: Catalin Marinas <catalin.marinas@....com>
> Reported-by: Linus Torvalds <torvalds@...ux-foundation.org>
> Signed-off-by: Will Deacon <will@...nel.org>

Reviewed-by: Catalin Marinas <catalin.marinas@....com>