mm/mremap: Add comment explaining the untagging behaviour of mremap()
commit b2a84de2 upstream. Commit dcde2373 ("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(). Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Reviewed-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Will Deacon <will@kernel.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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