[PATCH v3] mm/damon/reclaim: fix potential memory leak

[yahia]

From: yahia ahmed <yahia.a.abdrabou@xxxxxxxxx>

Fix a potential race condition by locking the ctx
then using damon_stop() to eliminate the thread then
destroy ctx.

Signed-off-by: yahia ahmed <yahia.a.abdrabou@xxxxxxxxx>
v3:
- Add a mutex lock to prevent possible race condition
- Stop the kdamond thread before destroying ctx
v2:
- Remove early return
- Set ctx to NULL to avoid a use after free
- Fix typo
---
 mm/damon/reclaim.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index 6601b08996c6..ec5558b7da41 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -480,6 +480,15 @@ static int __init damon_reclaim_init(void)
 		enabled = false;
 
 	if (err && ctx) {
+		/* Hold a lock and stop the thread to prevent a possible race condition */
+		mutex_lock(&ctx->kdamond_lock);
+
+		if (ctx->kdamond) {
+			mutex_unlock(&ctx->kdamond_lock);
+			damon_stop(ctx);
+		} else {
+			mutex_unlock(&ctx->kdamond_lock);
+		}
 		damon_destroy_ctx(ctx);
 		ctx = NULL;
 	}
-- 
2.54.0