diff options
authorDennis Zhou <>2019-02-21 15:54:11 -0800
committerDennis Zhou <>2019-03-13 12:25:31 -0700
commit8c43004af01635cc9fbb11031d070e5e0d327ef2 (patch)
parent8e5a2b9893f36457582596fdade10f6feb2797ee (diff)
percpu: do not search past bitmap when allocating an area
pcpu_find_block_fit() guarantees that a fit is found within PCPU_BITMAP_BLOCK_BITS. Iteration is used to determine the first fit as it compares against the block's contig_hint. This can lead to incorrectly scanning past the end of the bitmap. The behavior was okay given the check after for bit_off >= end and the correctness of the hints from pcpu_find_block_fit(). This patch fixes this by bounding the end offset by the number of bits in a chunk. Signed-off-by: Dennis Zhou <> Reviewed-by: Peng Fan <>
1 files changed, 2 insertions, 1 deletions
diff --git a/mm/percpu.c b/mm/percpu.c
index 938f295a60d4..769b7583975b 100644
--- a/mm/percpu.c
+++ b/mm/percpu.c
@@ -988,7 +988,8 @@ static int pcpu_alloc_area(struct pcpu_chunk *chunk, int alloc_bits,
* Search to find a fit.
- end = start + alloc_bits + PCPU_BITMAP_BLOCK_BITS;
+ end = min_t(int, start + alloc_bits + PCPU_BITMAP_BLOCK_BITS,
+ pcpu_chunk_map_bits(chunk));
bit_off = bitmap_find_next_zero_area(chunk->alloc_map, end, start,
alloc_bits, align_mask);
if (bit_off >= end)