[RFC PATCH 1/2] mm/damon/sysfs: dealloc repeat_call_control if damon_call() fails

[SeongJae Park <sj@kernel.org>]

damon_call() for repeat_call_control of DAMON_SYSFS could fail if
somehow the kdamond is stopped before the damon_call().  It could
happen, for example, when te damon context was made for monitroing of a
virtual address processes, and the process is terminated immediately,
before the damon_call() invocation.  In the case, the dyanmically
allocated repeat_call_control is not deallocated and leaked.

Fix the leak by deallocating the repeat_call_control under the
damon_call() failure.

This issue is discovered by sashiko [1].

[1] https://lore.kernel.org/20260320020630.962-1-sj@kernel.org

Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/sysfs.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c
index 6a44a2f3d8fc9..eefa959aa30ae 100644
--- a/mm/damon/sysfs.c
+++ b/mm/damon/sysfs.c
@@ -1670,7 +1670,8 @@ static int damon_sysfs_turn_damon_on(struct damon_sysfs_kdamond *kdamond)
 	repeat_call_control->data = kdamond;
 	repeat_call_control->repeat = true;
 	repeat_call_control->dealloc_on_cancel = true;
-	damon_call(ctx, repeat_call_control);
+	if (damon_call(ctx, repeat_call_control))
+		kfree(repeat_call_control);
 	return err;
 }
 
-- 
2.47.3