queue-4.19/percpu-do-not-search-past-bitmap-when-allocating-an-.patch

   1 From 98506788746933b7d1212684fc42e9798651d943 Mon Sep 17 00:00:00 2001
   2 From: Dennis Zhou <dennis@kernel.org>
   3 Date: Thu, 21 Feb 2019 15:54:11 -0800
   4 Subject: percpu: do not search past bitmap when allocating an area
   5
   6 [ Upstream commit 8c43004af01635cc9fbb11031d070e5e0d327ef2 ]
   7
   8 pcpu_find_block_fit() guarantees that a fit is found within
   9 PCPU_BITMAP_BLOCK_BITS. Iteration is used to determine the first fit as
  10 it compares against the block's contig_hint. This can lead to
  11 incorrectly scanning past the end of the bitmap. The behavior was okay
  12 given the check after for bit_off >= end and the correctness of the
  13 hints from pcpu_find_block_fit().
  14
  15 This patch fixes this by bounding the end offset by the number of bits
  16 in a chunk.
  17
  18 Signed-off-by: Dennis Zhou <dennis@kernel.org>
  19 Reviewed-by: Peng Fan <peng.fan@nxp.com>
  20 Signed-off-by: Sasha Levin <sashal@kernel.org>
  21 ---
  22  mm/percpu.c | 3 ++-
  23  1 file changed, 2 insertions(+), 1 deletion(-)
  24
  25 diff --git a/mm/percpu.c b/mm/percpu.c
  26 index c66149ce1fe6..ff76fa0b7528 100644
  27 --- a/mm/percpu.c
  28 +++ b/mm/percpu.c
  29 @@ -988,7 +988,8 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
  30         /*
  31          * Search to find a fit.
  32          */
  33 -       end = start + alloc_bits + PCPU_BITMAP_BLOCK_BITS;
  34 +       end = min_t(int, start + alloc_bits + PCPU_BITMAP_BLOCK_BITS,
  35 +                   pcpu_chunk_map_bits(chunk));
  36         bit_off = bitmap_find_next_zero_area(chunk->alloc_map, end, start,
  37                                              alloc_bits, align_mask);
  38         if (bit_off >= end)
  39 --
  40 2.20.1
  41