Messages in this thread Patch in this message | | | From | Greg Kroah-Hartman <> | Subject | [PATCH 3.18 04/12] mm/madvise.c: fix madvise() infinite loop under special circumstances | Date | Mon, 4 Dec 2017 16:59:18 +0100 |
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3.18-stable review patch. If anyone has any objections, please let me know.
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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 | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-)
--- a/mm/madvise.c +++ b/mm/madvise.c @@ -221,9 +221,9 @@ static long madvise_willneed(struct vm_a { 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 @@ -241,7 +241,6 @@ 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;
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