From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E45922C21DF; Wed, 9 Sep 2026 03:58:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788926302; cv=none; b=FXrGi9DCFu/bcqMCIY0NlLUR3HlPsUt09z2Wr1/uTJk+HChFZ9SwdlC99BExbFwGf7T5mbb/F2qgYVrZFPQYCDKoqI9vK7ew/CkxmOXCa4Cf6Q5+YXYMrFGAaF8bBDJy1zU1tXEstOOdq8NEDimsDZBThsxowidlG9/5OUxp9ok= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788926302; c=relaxed/simple; bh=1rXKRcayfCUzG/pJ3hvtS/+mr0jhA485O7zf3dSznjs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=cCxXM2icRvRM+SRreB76xiw/345juXWRo35xrTdtb79IVyX6NCazCtgIKX5f54rHy2T19fd2DJ7whS8sNAVu2y1MZfGKuraymBa4e6Nd4h0sfkA+g+LJ2aHowS4DD+4B67S32HUAVWmwR//e2ZX6YfkJPofzOijAlLL60DxARsg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=SroxVWwS; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="SroxVWwS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5846F1F00A3A; Wed, 9 Sep 2026 03:58:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1788926300; bh=8czkv2n5kUMtygHluIi/UGFt+ttscVsvIZlKrBI5TlA=; h=From:To:Cc:Subject:Date:In-Reply-To:References; b=SroxVWwSIRPeX5J/BFGnm5ATZAum/hlGNiDKbGZJ8BWUFgU85ddLIqrSedZnUz7SC WYOojQRs7NkxkBuBFqTNxnhd5UtNxNN96x7i66Q/Dp1CMtBv1PZnDW7GiF9jLuAt2n RkSDTw+riXp/f3Jch/nR3C4sEk+DFa9EJACw78CLZCunBjwU4NxkMqUclrpGfr7FgD VuUY8Y/vXu4Yd0J7lZbZtkDPFCSmwlKMyf2S0WbkZSa3DvvoYC8GO6qO98zpiKgHuH /HgEkP68RHoGDSu+ZkgS0X60jGPqi9VlA3CYakYx/BVlrVjGHB6h3njjtI5l914sMC KQvPUJV9Ta5rg== From: SJ Park To: stable@vger.kernel.org Cc: damon@lists.linux.dev, SJ Park , Brendan Higgins , Andrew Morton Subject: [PATCH 6.1.y] mm/damon/core-kunit: check region count before testing in split_at() Date: Tue, 8 Sep 2026 20:58:13 -0700 Message-ID: <20260909035813.162131-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <2026090820-envoy-endanger-c99b@gregkh> References: <2026090820-envoy-endanger-c99b@gregkh> Precedence: bulk X-Mailing-List: damon@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit damon_test_split_at() test next region that is assumed to be created by damon_split_region_at() invocation. But the split might fail. In this case, the succeeding test may dereference invalid pointers returned by damon_next_region(). The invalid pointer may not cause a really bad user impact, because of the implementation detail. It would only read wrong contents in the belonging damon_target struct. Depending on the future change of the offset from the link header to the accessing field, this could also be really dangerous, though. Still, the realistic user impact would be limited. It would affect only test run setups. Fix it by testing if the number of regions was also changed as expected and exit early for the failure. The issue was discovered [1] by Sashiko. Link: https://lore.kernel.org/20260718001442.87129-3-sj@kernel.org Link: https://lore.kernel.org/20260714142352.100478-1-sj@kernel.org [1] Fixes: 17ccae8bb5c9 ("mm/damon: add kunit tests") Signed-off-by: SJ Park Cc: Brendan Higgins Cc: # 5.15.x Signed-off-by: Andrew Morton (cherry picked from commit 9b18ef3c3aa1ce24176e340061caf15fa2742564) Signed-off-by: SJ Park --- mm/damon/core-test.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/mm/damon/core-test.h b/mm/damon/core-test.h index d8fef225930a5..1dd17d43a642c 100644 --- a/mm/damon/core-test.h +++ b/mm/damon/core-test.h @@ -162,6 +162,9 @@ static void damon_test_split_at(struct kunit *test) } damon_add_region(r, t); damon_split_region_at(t, r, 25); + KUNIT_EXPECT_EQ(test, damon_nr_regions(t), 2); + if (!damon_nr_regions(t) != 2) + goto out; KUNIT_EXPECT_EQ(test, r->ar.start, 0ul); KUNIT_EXPECT_EQ(test, r->ar.end, 25ul); @@ -169,6 +172,7 @@ static void damon_test_split_at(struct kunit *test) KUNIT_EXPECT_EQ(test, r->ar.start, 25ul); KUNIT_EXPECT_EQ(test, r->ar.end, 100ul); +out: damon_free_target(t); damon_destroy_ctx(c); } -- 2.47.3