From nobody Mon Apr 6 11:53:09 2026 Received: from sender-of-o55.zoho.eu (sender-of-o55.zoho.eu [136.143.169.55]) (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 AB0D33E9582 for ; Thu, 19 Mar 2026 15:58:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=pass smtp.client-ip=136.143.169.55 ARC-Seal: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773935884; cv=pass; b=mYdUYtb6wBLBl2N7kJCLLyMSrmky0pwC0Kr2EzdN6RsYG9brOKbEaG2nnSHTdbGExeVvpF9OBcafWkXUVfhfmmt/BJtoxMOOpOt90F0QIhXMYaBhs1dAmmW6BvL6Kmuz5bqQzt2DVS5XEmajn1tFDOEA3qR/u6ta14tUiqz9g7I= ARC-Message-Signature: i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773935884; c=relaxed/simple; bh=HNOP+AY8Je/ylVxnYb9OPN9PISdxkUDu1/hSxGJc1L8=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=Ga0MBBBtIee6Ue2mFLHdCPi8yrl4986dO6nwTinjAoMlv0C5zdsqWp9g/bcD5EjhUMHraCHlnA6n2bbFLYx28wvF6i+eAzwnNTuFbcdis3SGSwfk0VNmXi8S9nWBtI9Y+D+WG6iqorVgaoxMBLKwBowoCKiOjC7r5ywL3MR+KxU= 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=J0IrkYMM; arc=pass smtp.client-ip=136.143.169.55 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="J0IrkYMM" ARC-Seal: i=1; a=rsa-sha256; t=1773935868; cv=none; d=zohomail.eu; s=zohoarc; b=CI9a1WdQDHNBO5LmDiXZ+zHg1T9l5jwDZAg9PiwfQxq60i/JHTriM5qT08U8oPIcxQD26D8OssOazDGQh8+5JiLTVu1Tyx6aEdtVVYlEJA+ja2bMOz6vlOKOzKYXwsDeJBi8e0oOlw6MT4bbE90irrgA3wW9+b1t0KMkGuLg/Ao= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zohomail.eu; s=zohoarc; t=1773935868; 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=yqwjs8HCz1qaJbZTaGQP4LkV0ZgUX/+x9dm2bkSNu3k=; b=WWwwFzjHBE33VKmmHAu1r8RiQU+XbxBxfobcBz34crIsg3KHmQGau1yDNyvcWPI6xTvJkBwPqKmN2rdJy9RW6ZfGhVFS0x0hRkxws3Z+gu2ypOzg66auQRUXUrI8nGmWqgNYTHTApj5kNEVrzXxnlgM4CSQm4KWC2OdL+kCeOaY= 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=1773935868; 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=yqwjs8HCz1qaJbZTaGQP4LkV0ZgUX/+x9dm2bkSNu3k=; b=J0IrkYMMDk78IqYe33PNM3IEF1/Ei8kjFJj8ruD+Q6IEByNziVn+7nB6vKUwWBjS 4ZJV6b9ItM3eFui+GVQDebf0Ry0MLpXpJM2PH1tR5sLIPfGP0DWtQ9kCYAU8xftu9BF u5FQxWjWJvZ8nSD7wt6LmItfc6hVnTBIzdV9eh/Y= Received: by mx.zoho.eu with SMTPS id 1773935866558314.7705252149991; Thu, 19 Mar 2026 16:57:46 +0100 (CET) From: Josh Law To: sj@kernel.org, akpm@linux-foundation.org Cc: damon@lists.linux.dev, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Josh Law Subject: [PATCH 4/4] mm/damon/sysfs: check contexts->nr in repeat_call_fn Date: Thu, 19 Mar 2026 15:57:42 +0000 Message-Id: <20260319155742.186627-5-objecting@objecting.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20260319155742.186627-1-objecting@objecting.org> References: <20260319155742.186627-1-objecting@objecting.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-ZohoMailClient: External Content-Type: text/plain; charset="utf-8" damon_sysfs_repeat_call_fn() accesses contexts_arr[0] in upd_tuned_intervals, upd_schemes_stats, and upd_schemes_effective_quotas without checking nr_contexts. A user can set nr_contexts to 0 via sysfs while DAMON is running, causing a NULL pointer dereference in the repeat callback. Add a guard under the lock. 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 ddcdc4e35b27..d982f2dc7a2b 100644 --- a/mm/damon/sysfs.c +++ b/mm/damon/sysfs.c @@ -1620,9 +1620,12 @@ static int damon_sysfs_repeat_call_fn(void *data) =20 if (!mutex_trylock(&damon_sysfs_lock)) return 0; + if (sysfs_kdamond->contexts->nr !=3D 1) + goto out; damon_sysfs_upd_tuned_intervals(sysfs_kdamond); damon_sysfs_upd_schemes_stats(sysfs_kdamond); damon_sysfs_upd_schemes_effective_quotas(sysfs_kdamond); +out: mutex_unlock(&damon_sysfs_lock); return 0; } --=20 2.34.1