From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sender-of-o57.zoho.eu (sender-of-o57.zoho.eu [136.143.169.57]) (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 A83EC36EAB7; Fri, 20 Mar 2026 16:35:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.169.57 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774024518; cv=pass; b=GMNMMuDD3tdg1oPR0sJ+LKeoVyiJAEuczXybPEcOj4fN6v3cUcsNlLsIMK/ULmsPX1OIg/wBvFNY6YKOSXSpo9lpRO91kMPjYq1gvMApoaCFGikkk7tVR+ZZDK5gdDdidoeDp0QRk0f7eOvuz3RCQixF28mxdv1Bd4yq26MYkXI= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774024518; c=relaxed/simple; bh=rXBnjOpdM4Zz9KkgGNRIZmxPV6JW3HhGTuomv2aKen8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=mg863t+i/kNX4TF8fLq1Qc5r+svYAewtYXe24HLQriyU5uv6WnrJ+IVhOsg5lvqyUBEVV1QH52GZGGVoQ1nhBryfeAKsaiqJ7y/Ih+sGPwWMrOBgyIDJBaAxZd6uzIatg53Bk+Z534ODOkvrB9MjBDcNjj7FGeQEkSpPlWIijkw= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=objecting.org; spf=pass smtp.mailfrom=objecting.org; dkim=pass (1024-bit key) header.d=objecting.org header.i=objecting@objecting.org header.b=IQcW4itx; arc=pass smtp.client-ip=136.143.169.57 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=objecting.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=objecting.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=objecting.org header.i=objecting@objecting.org header.b="IQcW4itx" ARC-Seal: i=1; a=rsa-sha256; t=1774024502; cv=none; d=zohomail.eu; s=zohoarc; b=AM95RR5uphhvbypB5zZcKQyuhQk7YMVitMyutExXVXZ+078ZMhENcqQ4t4t5bYAAnhKUTNlitxmlXxvKYgIB6SIw69NG0mqK8yRCcXu2EbwUaklxT/oGNdGSsr/9QkTVkt2nMxB8kIlDvWiH+y9aY3txUm6wzT+UBXkO9syUsf0= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.eu; s=zohoarc; t=1774024502; h=Content-Transfer-Encoding:Cc:Cc:Date:Date:From:From:In-Reply-To:MIME-Version:Message-ID:References:Subject:Subject:To:To:Message-Id:Reply-To; bh=xBhz+FP718xfFTo+Jqt21ir9B4N+Sz9WG+S91iYYSqU=; b=cuDy398xA/BZzFaZTgMof76ZrElybYuGUf8hItLNkdOBCv9YkNMptn2/xf8hQUQLPBdyMXpX8TflzaI+5oa34xe0ezAruNWVe5dzhLWarbJzsMAm/gEhxxoLd5lWDVZgWAZ36h5Xjw8jl3prxuduCTIQ7IUbOzPGKVZ3X+rSmmg= ARC-Authentication-Results: i=1; mx.zohomail.eu; dkim=pass header.i=objecting.org; spf=pass smtp.mailfrom=objecting@objecting.org; dmarc=pass header.from= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1774024502; s=zmail; d=objecting.org; i=objecting@objecting.org; h=From:From:To:To:Cc:Cc:Subject:Subject:Date:Date:Message-Id:Message-Id:In-Reply-To:References:MIME-Version:Content-Transfer-Encoding:Reply-To; bh=xBhz+FP718xfFTo+Jqt21ir9B4N+Sz9WG+S91iYYSqU=; b=IQcW4itxhvSjAeWAkGS291o2DHx7pM5CdohtNSGbnTqxs+WUqdeJwdjvurN/QrpW 04Lvw8t/1GQZclHqSlX7vM6OJANpq4L5JYkNSah0AKN4XpDYA11S3h1UFaRbcil6cVS WprZNJxRuvTKTHqmGgHi+sYFNzb2Kztm4LtMQm+M= Received: by mx.zoho.eu with SMTPS id 1774024498762636.5600957673564; Fri, 20 Mar 2026 17:34:58 +0100 (CET) From: Josh Law To: SeongJae Park , Andrew Morton Cc: damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Josh Law , stable@vger.kernel.org Subject: [PATCH v2] mm/damon/sysfs: check contexts->nr before accessing contexts_arr[0] Date: Fri, 20 Mar 2026 16:34:55 +0000 Message-Id: <20260320163456.177750-2-objecting@objecting.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260320163456.177750-1-objecting@objecting.org> References: <20260320163456.177750-1-objecting@objecting.org> Precedence: bulk X-Mailing-List: stable@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-ZohoMailClient: External Multiple sysfs command paths dereference contexts_arr[0] without first verifying that nr_contexts >= 1. A user can set nr_contexts to 0 via sysfs while DAMON is running, causing NULL pointer dereferences. Guard all commands (except OFF) at the entry point of damon_sysfs_handle_cmd(). Fixes: 0ac32b8affb5 ("mm/damon/sysfs: support DAMOS stats") Cc: # 5.18.x Signed-off-by: Josh Law Reviewed-by: SeongJae Park --- mm/damon/sysfs.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/mm/damon/sysfs.c b/mm/damon/sysfs.c index b573b9d60784..ddc30586c0e6 100644 --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -1749,6 +1749,9 @@ static int damon_sysfs_update_schemes_tried_regions( static int damon_sysfs_handle_cmd(enum damon_sysfs_cmd cmd, struct damon_sysfs_kdamond *kdamond) { + if (cmd != DAMON_SYSFS_CMD_OFF && kdamond->contexts->nr != 1) + return -EINVAL; + switch (cmd) { case DAMON_SYSFS_CMD_ON: return damon_sysfs_turn_damon_on(kdamond); -- 2.34.1