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

Catalin Marinas
2020-03-25T11:23:15Z

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@arm.com>
> Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
> Signed-off-by: Will Deacon <will@kernel.org>

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