[PATCH] /dev/zero vs hugetlb mappings.
Hugetlbfs mmap with MAP_PRIVATE becomes MAP_SHARED silently, but vma->vm_flags have no VM_SHARED bit. Reading from /dev/zero into hugetlb area will do: read_zero() read_zero_pagealigned() if (vma->vm_flags & VM_SHARED) break; // fallback to clear_user() zap_page_range(); zeromap_page_range(); It will hit BUG_ON() in unmap_hugepage_range() if region is not huge page aligned, or silently convert it into the private anonymous mapping. Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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