Commit 6ea8d958 authored Nov 29, 2017 by chenjie Committed by Linus Torvalds Nov 29, 2017

mm/madvise.c: fix madvise() infinite loop under special circumstances

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: fe77ba6f ("[PATCH] xip: madvice/fadvice: execute in place")
Signed-off-by: chenjie <chenjie6@huawei.com>
Signed-off-by: guoxuenan <guoxuenan@huawei.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: zhangyi (F) <yi.zhang@huawei.com>
Cc: Miao Xie <miaoxie@huawei.com>
Cc: Mike Rapoport <rppt@linux.vnet.ibm.com>
Cc: Shaohua Li <shli@fb.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Carsten Otte <cotte@de.ibm.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 04e35f44

mm/madvise.c

+1 −3

Original line number	Diff line number	Diff line
		@@ -276,15 +276,14 @@ static long madvise_willneed(struct vm_area_struct *vma,
		{
		struct file *file = vma->vm_file;

		*prev = vma;
		#ifdef CONFIG_SWAP
		if (!file) {
		*prev = vma;
		force_swapin_readahead(vma, start, end);
		return 0;
		}

		if (shmem_mapping(file->f_mapping)) {
		*prev = vma;
		force_shm_swapin_readahead(vma, start, end,
		file->f_mapping);
		return 0;
		@@ -299,7 +298,6 @@ 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;

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