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zsmalloc: reset compaction source zspage pointer after putback_zspage()

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The current implementation of the compaction loop fails to set the source
zspage pointer to NULL in all cases, leading to a potential issue where
__zs_compact() could use a stale zspage pointer.  This pointer could even
point to a previously freed zspage, causing unexpected behavior in the
putback_zspage() and migrate_write_unlock() functions after returning from
the compaction loop.

Address the issue by ensuring that the source zspage pointer is always set
to NULL when it should be.

Link: https://lkml.kernel.org/r/20230417130850.1784777-1-senozhatsky@chromium.org
Fixes: 5a845e9f2d ("zsmalloc: rework compaction algorithm")
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Reported-by: Yu Zhao <yuzhao@google.com>
Tested-by: Yu Zhao <yuzhao@google.com>
Reviewed-by: Yosry Ahmed <yosryahmed@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Sergey Senozhatsky 2023-04-17 22:08:50 +09:00 committed by Andrew Morton
parent 5f300fd59a
commit f7ddb61256
1 changed files with 1 additions and 1 deletions
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2
mm/zsmalloc.c
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@ -2239,8 +2239,8 @@ static unsigned long __zs_compact(struct zs_pool *pool,
if (fg == ZS_INUSE_RATIO_0) {
free_zspage(pool, class, src_zspage);
pages_freed += class->pages_per_zspage;
src_zspage = NULL;
}
src_zspage = NULL;
if (get_fullness_group(class, dst_zspage) == ZS_INUSE_RATIO_100
|| spin_is_contended(&pool->lock)) {