From 23aaed6659df9adfabe9c583e67a36b54e21df46 Mon Sep 17 00:00:00 2001 From: Shiraz Hashim Date: Thu, 5 Feb 2015 12:25:06 -0800 Subject: [PATCH] mm: pagewalk: call pte_hole() for VM_PFNMAP during walk_page_range walk_page_range() silently skips vma having VM_PFNMAP set, which leads to undesirable behaviour at client end (who called walk_page_range). Userspace applications get the wrong data, so the effect is like just confusing users (if the applications just display the data) or sometimes killing the processes (if the applications do something with misunderstanding virtual addresses due to the wrong data.) For example for pagemap_read, when no callbacks are called against VM_PFNMAP vma, pagemap_read may prepare pagemap data for next virtual address range at wrong index. Eventually userspace may get wrong pagemap data for a task. Corresponding to a VM_PFNMAP marked vma region, kernel may report mappings from subsequent vma regions. User space in turn may account more pages (than really are) to the task. In my case I was using procmem, procrack (Android utility) which uses pagemap interface to account RSS pages of a task. Due to this bug it was giving a wrong picture for vmas (with VM_PFNMAP set). Fixes: a9ff785e4437 ("mm/pagewalk.c: walk_page_range should avoid VM_PFNMAP areas") Signed-off-by: Shiraz Hashim Acked-by: Naoya Horiguchi Cc: [3.10+] Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/pagewalk.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) diff --git a/mm/pagewalk.c b/mm/pagewalk.c index ad83195521f2..b264bda46e1b 100644 --- a/mm/pagewalk.c +++ b/mm/pagewalk.c @@ -199,7 +199,10 @@ int walk_page_range(unsigned long addr, unsigned long end, */ if ((vma->vm_start <= addr) && (vma->vm_flags & VM_PFNMAP)) { - next = vma->vm_end; + if (walk->pte_hole) + err = walk->pte_hole(addr, next, walk); + if (err) + break; pgd = pgd_offset(walk->mm, next); continue; } -- 2.20.1