releases/4.4.177/assoc_array-fix-shortcut-creation.patch

   1 From c5fe03ac40ae7f2d86ce613f3d7e24569ec60f01 Mon Sep 17 00:00:00 2001
   2 From: David Howells <dhowells@redhat.com>
   3 Date: Thu, 14 Feb 2019 16:20:15 +0000
   4 Subject: assoc_array: Fix shortcut creation
   5
   6 [ Upstream commit bb2ba2d75a2d673e76ddaf13a9bd30d6a8b1bb08 ]
   7
   8 Fix the creation of shortcuts for which the length of the index key value
   9 is an exact multiple of the machine word size.  The problem is that the
  10 code that blanks off the unused bits of the shortcut value malfunctions if
  11 the number of bits in the last word equals machine word size.  This is due
  12 to the "<<" operator being given a shift of zero in this case, and so the
  13 mask that should be all zeros is all ones instead.  This causes the
  14 subsequent masking operation to clear everything rather than clearing
  15 nothing.
  16
  17 Ordinarily, the presence of the hash at the beginning of the tree index key
  18 makes the issue very hard to test for, but in this case, it was encountered
  19 due to a development mistake that caused the hash output to be either 0
  20 (keyring) or 1 (non-keyring) only.  This made it susceptible to the
  21 keyctl/unlink/valid test in the keyutils package.
  22
  23 The fix is simply to skip the blanking if the shift would be 0.  For
  24 example, an index key that is 64 bits long would produce a 0 shift and thus
  25 a 'blank' of all 1s.  This would then be inverted and AND'd onto the
  26 index_key, incorrectly clearing the entire last word.
  27
  28 Fixes: 3cb989501c26 ("Add a generic associative array implementation.")
  29 Signed-off-by: David Howells <dhowells@redhat.com>
  30 Signed-off-by: James Morris <james.morris@microsoft.com>
  31 Signed-off-by: Sasha Levin <sashal@kernel.org>
  32 ---
  33  lib/assoc_array.c | 8 +++++---
  34  1 file changed, 5 insertions(+), 3 deletions(-)
  35
  36 diff --git a/lib/assoc_array.c b/lib/assoc_array.c
  37 index 5cd093589c5a..3b46c5433b7a 100644
  38 --- a/lib/assoc_array.c
  39 +++ b/lib/assoc_array.c
  40 @@ -781,9 +781,11 @@ all_leaves_cluster_together:
  41                 new_s0->index_key[i] =
  42                         ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE);
  43
  44 -       blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
  45 -       pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);
  46 -       new_s0->index_key[keylen - 1] &= ~blank;
  47 +       if (level & ASSOC_ARRAY_KEY_CHUNK_MASK) {
  48 +               blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK);
  49 +               pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank);
  50 +               new_s0->index_key[keylen - 1] &= ~blank;
  51 +       }
  52
  53         /* This now reduces to a node splitting exercise for which we'll need
  54          * to regenerate the disparity table.
  55 --
  56 2.19.1
  57