FAILED: patch "[PATCH] mm/damon/core: disallow non-power of two min_region_sz on" failed to apply to 6.18-stable tree

The patch below does not apply to the 6.18-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.18.y
git checkout FETCH_HEAD
git cherry-pick -x 95093e5cb4c5b50a5b1a4b79f2942b62744bd66a
# <resolve conflicts, build, test, etc.>
git commit -s
git send-email --to '<[email protected]>' --in-reply-to '2026050357-senator-aroma-1859@gregkh' --subject-prefix 'PATCH 6.18.y' HEAD^..

Possible dependencies:

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 95093e5cb4c5b50a5b1a4b79f2942b62744bd66a Mon Sep 17 00:00:00 2001
From: SeongJae Park <[email protected]>
Date: Sat, 11 Apr 2026 14:36:36 -0700
Subject: [PATCH] mm/damon/core: disallow non-power of two min_region_sz on
damon_start()

Commit d8f867fa0825 ("mm/damon: add damon_ctx->min_sz_region") introduced a bug that allows unaligned DAMON region address ranges. Commit c80f46ac228b ("mm/damon/core: disallow non-power of two min_region_sz") fixed it, but only for damon_commit_ctx() use case. Still, DAMON sysfs interface can emit non-power of two min_region_sz via damon_start(). Fix the path by adding the is_power_of_2() check on damon_start().

The issue was discovered by sashiko [1].

index 3703f62a876b..c107d74c77e7 100644
@@ -1368,6 +1368,11 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs, bool exclusive)
 	int i;
 	int err = 0;
 
+	for (i = 0; i < nr_ctxs; i++) {
+		if (!is_power_of_2(ctxs[i]->min_region_sz))
+			return -EINVAL;
+	}
+
 	mutex_lock(&damon_lock);
 	if ((exclusive && nr_running_ctxs) ||
 			(!exclusive && running_exclusive_ctxs)) {

Commit d8f867fa0825 ("mm/damon: add damon_ctx->min_sz_region") introduced a bug that allows unaligned DAMON region address ranges. Commit c80f46ac228b ("mm/damon/core: disallow non-power of two min_region_sz") fixed it, but only for damon_commit_ctx() use case. Still, DAMON sysfs interface can emit non-power of two min_region_sz via damon_start(). Fix the path by adding the is_power_of_2() check on damon_start().

The issue was discovered by sashiko [1].

---
 mm/damon/core.c | 5 +++++
 1 file changed, 5 insertions(+)

index 87b6c9c2d647..e016ca7fde5e 100644
@@ -1352,6 +1352,11 @@ int damon_start(struct damon_ctx **ctxs, int nr_ctxs, bool exclusive)
 	int i;
 	int err = 0;
 
+	for (i = 0; i < nr_ctxs; i++) {
+		if (!is_power_of_2(ctxs[i]->min_sz_region))
+			return -EINVAL;
+	}
+
 	mutex_lock(&damon_lock);
 	if ((exclusive && nr_running_ctxs) ||
 			(!exclusive && running_exclusive_ctxs)) {

2.47.3