[RFC PATCH 1/2] mm/damon/reclaim: handle ctx allocation failure

[SeongJae Park <sj@kernel.org>]

DAMON_RECLAIM allocates the damon_ctx object for its kdamond in its init
function.  damon_reclaim_enabled_store() wrongly assumes the allocation
will always succeed once tried.  If the damon_ctx allocation was failed,
therefore, code execution reaches to damon_commit_ctx() while 'ctx' is
NULL.  As a result, it dereferences the NULL 'ctx' pointer.  Avoid the
NULL dereference by returning -ENOMEM if 'ctx' is NULL.

Fixes: 3f7a914ab9a5 ("mm/damon/reclaim: use damon_initialized()")
Cc: <stable@vger.kernel.org> # 6.18.x
Signed-off-by: SeongJae Park <sj@kernel.org>
---
 mm/damon/reclaim.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mm/damon/reclaim.c b/mm/damon/reclaim.c
index ed446d00ef1cf..ce4499cf4b8b0 100644
--- a/mm/damon/reclaim.c
+++ b/mm/damon/reclaim.c
@@ -399,6 +399,10 @@ static int damon_reclaim_enabled_store(const char *val,
 	if (!damon_initialized())
 		return 0;
 
+	/* damon_modules_new_paddr_ctx_target() in the init function failed. */
+	if (!ctx)
+		return -ENOMEM;
+
 	return damon_reclaim_turn(enabled);
 }
 
-- 
2.47.3