4.9-stable review patch. If anyone has any objections, please let me know.
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[ Upstream commit bb2ba2d75a2d673e76ddaf13a9bd30d6a8b1bb08 ]
Fix the creation of shortcuts for which the length of the index key value is an exact multiple of the machine word size. The problem is that the code that blanks off the unused bits of the shortcut value malfunctions if the number of bits in the last word equals machine word size. This is due to the "<<" operator being given a shift of zero in this case, and so the mask that should be all zeros is all ones instead. This causes the subsequent masking operation to clear everything rather than clearing nothing.
Ordinarily, the presence of the hash at the beginning of the tree index key makes the issue very hard to test for, but in this case, it was encountered due to a development mistake that caused the hash output to be either 0 (keyring) or 1 (non-keyring) only. This made it susceptible to the keyctl/unlink/valid test in the keyutils package.
The fix is simply to skip the blanking if the shift would be 0. For example, an index key that is 64 bits long would produce a 0 shift and thus a 'blank' of all 1s. This would then be inverted and AND'd onto the index_key, incorrectly clearing the entire last word.
Fixes: 3cb989501c26 ("Add a generic associative array implementation.") Signed-off-by: David Howells dhowells@redhat.com Signed-off-by: James Morris james.morris@microsoft.com Signed-off-by: Sasha Levin sashal@kernel.org --- lib/assoc_array.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/lib/assoc_array.c b/lib/assoc_array.c index 5cd093589c5a..3b46c5433b7a 100644 --- a/lib/assoc_array.c +++ b/lib/assoc_array.c @@ -781,9 +781,11 @@ all_leaves_cluster_together: new_s0->index_key[i] = ops->get_key_chunk(index_key, i * ASSOC_ARRAY_KEY_CHUNK_SIZE);
- blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK); - pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank); - new_s0->index_key[keylen - 1] &= ~blank; + if (level & ASSOC_ARRAY_KEY_CHUNK_MASK) { + blank = ULONG_MAX << (level & ASSOC_ARRAY_KEY_CHUNK_MASK); + pr_devel("blank off [%zu] %d: %lx\n", keylen - 1, level, blank); + new_s0->index_key[keylen - 1] &= ~blank; + }
/* This now reduces to a node splitting exercise for which we'll need * to regenerate the disparity table.