This is a note to let you know that I've just added the patch titled

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

to the 4.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: mm-madvise.c-fix-madvise-infinite-loop-under-special-circumstances.patch and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From 6ea8d958a2c95a1d514015d4e29ba21a8c0a1a91 Mon Sep 17 00:00:00 2001

From: chenjie chenjie6@huawei.com Date: Wed, 29 Nov 2017 16:10:54 -0800 Subject: mm/madvise.c: fix madvise() infinite loop under special circumstances

From: chenjie chenjie6@huawei.com

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 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 Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Linus Torvalds torvalds@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

--- mm/madvise.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)

--- a/mm/madvise.c +++ b/mm/madvise.c @@ -223,15 +223,14 @@ static long madvise_willneed(struct vm_a { 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; @@ -246,7 +245,6 @@ static long madvise_willneed(struct vm_a return 0; }

- *prev = vma; start = ((start - vma->vm_start) >> PAGE_SHIFT) + vma->vm_pgoff; if (end > vma->vm_end) end = vma->vm_end;

Patches currently in stable-queue which might be from chenjie6@huawei.com are

queue-4.4/mm-madvise.c-fix-madvise-infinite-loop-under-special-circumstances.patch