lkml.org 
[lkml]   [2019]   [Feb]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 02/12] percpu: do not search past bitmap when allocating an area
Date
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 <dennis@kernel.org>
---
mm/percpu.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/percpu.c b/mm/percpu.c
index 53bd79a617b1..69ca51d238b5 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)
--
2.17.1
\
 
 \ /
  Last update: 2019-02-28 03:20    [W:0.139 / U:50.852 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site