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 A25DD39A803; Fri, 20 Mar 2026 16:36:17 +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=1774024579; cv=pass; b=rHxyK8uiHQXKV8Z4BjFvVMRZK8AO2R3pZWxIoahLwCFoja6z7aydf3VHY7yRe1ggkEd7skeheC2ttEmBMQkwcVq+jpAcqjZhuFs7v9+24jrfp8mC0w5zsOwXtXGlcwLUJotFTxeE4gJPnbjoNnxOHWKLg5lXILD1/yUzHbAgjdo= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774024579; c=relaxed/simple; bh=rXBnjOpdM4Zz9KkgGNRIZmxPV6JW3HhGTuomv2aKen8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=aPbVMewKJ1TYY//Q2vY9l99pNX/S0XgYajd883uzBfNNhBE5fyj3OYn6PfnpYNytHh8geZzxEcsIJy3pmAvsGxcltIjwbnHw9J61hBFBLcC4fyHVpb/nkVUTEC7glI40Ba/P74WAICpNgoNB+A8kUHux6FH58FeBvjgqRe3bq0w= 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=I+rSrwmd; 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="I+rSrwmd" ARC-Seal: i=1; a=rsa-sha256; t=1774024563; cv=none; d=zohomail.eu; s=zohoarc; b=ff8X3tljHjklyFzeIFOMCAdNbLmebNvpYED9ZqvO5oAD7NDG1a45ss15UN6rHaeUpEF87bR6hsw4wmrIsW2j4KmhzuOc7YqAQmp49YiORUQdPIhzYlGKnYBxHdBY6IvtkY15H0jjAhxHRjbrnZfAMb0ojGsK1vvlG2ydZXgLss0= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.eu; s=zohoarc; t=1774024563; 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=Et+EfbnAdIfTOdfn2PjpJQeP4ypoP4uxvfKy9C1+AVGQSrKOzpFxuK7BPala0qvsStG2h0MF5C9Vz0ZZBbUMHrev2ZelqjEqefje9uXmFIr7pMwMhYnilH65aFwi3j1ZEFivFfdGiaZRrG4H54WJnbRnJm0P6hbq1y5HQZiyQUg= 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=1774024563; 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=I+rSrwmdO5diJIt0LdFNl3Yk3dlXhjTt0x0zyF30VEYe6opl27xXPDSUJJ3tXuYj 1CMYjf3lBkYeKUDR3YP7NTyVHGex8JG3e8me/ea7fJzJV7H4XsLbLeKHaO5n+mTseGj 7/xRFtAU2A4eivvzCxi6s6B3sCWpX/vEWTlm4eh0= Received: by mx.zoho.eu with SMTPS id 1774024562167191.42267947695075; Fri, 20 Mar 2026 17:36:02 +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 2/3] mm/damon/sysfs: check contexts->nr before accessing contexts_arr[0] Date: Fri, 20 Mar 2026 16:35:58 +0000 Message-Id: <20260320163559.178101-2-objecting@objecting.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260320163559.178101-1-objecting@objecting.org> References: <20260320163559.178101-1-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