From 38a4a0bdb663cfe435aaa9be0fc77c0850408e1f Mon Sep 17 00:00:00 2001 From: chenjie Date: Wed, 29 Nov 2017 16:10:54 -0800 Subject: [PATCH] mm/madvise.c: fix madvise() infinite loop under special circumstances commit 6ea8d958a2c95a1d514015d4e29ba21a8c0a1a91 upstream. MADVISE_WILLNEED has always been a noop for DAX (formerly XIP) mappings. Unfortunately madvise_willneed() doesn't communicate this information properly to the generic madvise syscall implementation. The calling convention is quite subtle there. madvise_vma() is supposed to either return an error or update &prev otherwise the main loop will never advance to the next vma and it will keep looping for ever without a way to get out of the kernel. It seems this has been broken since introduction. Nobody has noticed because nobody seems to be using MADVISE_WILLNEED on these DAX mappings. [mhocko@suse.com: rewrite changelog] Link: http://lkml.kernel.org/r/20171127115318.911-1-guoxuenan@huawei.com Fixes: fe77ba6f4f97 ("[PATCH] xip: madvice/fadvice: execute in place") Signed-off-by: chenjie Signed-off-by: guoxuenan Acked-by: Michal Hocko Cc: Minchan Kim Cc: zhangyi (F) Cc: Miao Xie Cc: Mike Rapoport Cc: Shaohua Li Cc: Andrea Arcangeli Cc: Mel Gorman Cc: Kirill A. Shutemov Cc: David Rientjes Cc: Anshuman Khandual Cc: Rik van Riel Cc: Carsten Otte Cc: Dan Williams Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/madvise.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/mm/madvise.c b/mm/madvise.c index 85d1a5427c27..85580e1000fa 100644 --- a/mm/madvise.c +++ b/mm/madvise.c @@ -222,9 +222,9 @@ static long madvise_willneed(struct vm_area_struct * vma, { struct file *file = vma->vm_file; + *prev = vma; #ifdef CONFIG_SWAP if (!file || mapping_cap_swap_backed(file->f_mapping)) { - *prev = vma; if (!file) force_swapin_readahead(vma, start, end); else @@ -242,7 +242,6 @@ static long madvise_willneed(struct vm_area_struct * vma, return 0; } - *prev = vma; start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; if (end > vma->vm_end) end = vma->vm_end;