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Thu, 13 Aug 2026 16:32:55 +0800 (CST) Received: from mscpeml500003.china.huawei.com (unknown [7.188.49.51]) by mail.maildlp.com (Postfix) with ESMTPS id 434DA40575; Thu, 13 Aug 2026 16:33:03 +0800 (CST) Received: from [10.123.123.154] (10.123.123.154) by mscpeml500003.china.huawei.com (7.188.49.51) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.2.2562.45; Thu, 13 Aug 2026 11:33:02 +0300 Message-ID: Date: Thu, 13 Aug 2026 11:33:01 +0300 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/4] mm/damon/core: handle NULL ctx parameter in damon_call() To: SJ Park CC: Andrew Morton , , , References: <20260813035001.97364-1-sj@kernel.org> <20260813035001.97364-2-sj@kernel.org> Content-Language: en-US From: Gutierrez Asier In-Reply-To: <20260813035001.97364-2-sj@kernel.org> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.123.123.154] X-ClientProxiedBy: mscpeml100003.china.huawei.com (10.199.174.67) To mscpeml500003.china.huawei.com (7.188.49.51) X-Stat-Signature: jt8acwou6q3s5oe3xoeh4ixbcs8uur69 X-Rspamd-Queue-Id: 7F85C40004 X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1786609989-72144 X-HE-Meta: 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 aR93+Dmk dQCNDAkkAZhW7r55yJZQOIrkpYbnI+51L8JMdPRAbNZQKOIOTsLNKcgpt4+Nsjv2d7Dmi8dT6OA4bowU1Fp+5kRFUphnJ2KiideKyolMT5PSZL8zBctl9JYg3uUC3qbA+dPMC3HbAw7wCu8sSlHC836PRTUsVdG4K6B2cW7jhDhN21u4CQmeytVVqsbPWed4sEcWjaSO8SfUMx9Dwb9O92ov/Z798W2w4LUfOsxn3P2r6jmICJcT1MRMZjCq++dFQ6O/cLduQBB/I0SCR2vRdwlpfdJREYZNXOX+a/gMnPd3zUQCMnzBP36I+5GIzD1Oh5RFX3FlDbMlafTbhTdtZTGFGMlS2T0e3bloIbwvYM/Hf6lJ4Fx/gnlpp3VpmTsJH/tr5V3cfmvWrxAztKUapJr/9RB2uGF7Qq7gp Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Hi SJ, On 8/13/2026 6:49 AM, SJ Park wrote: > When NULL damon_ctx pointer parameter is passed, damon_call() could do > NULL dereference. The caller is responsible to avoid that. It is easy > to forget, and there are many damon_call() callers. Meanwhile, > damon_call() is never meant to be performance critical. It uses mutex > and completion. Add the NULL pointer check inside damon_call() so that > callers can pass the parameter without NULL checks. > > Signed-off-by: SJ Park > --- > mm/damon/core.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/mm/damon/core.c b/mm/damon/core.c > index 92631a36d7b51..5882f9c94c47f 100644 > --- a/mm/damon/core.c > +++ b/mm/damon/core.c > @@ -2188,6 +2188,8 @@ int damon_kdamond_pid(struct damon_ctx *ctx) > */ > int damon_call(struct damon_ctx *ctx, struct damon_call_control *control) > { > + if (!ctx) > + return -EINVAL; > if (!control->repeat) > init_completion(&control->completion); > control->canceled = false; I know that this is a minor optimization, but how about moving INIT_LIST_HEAD(&control->list) to right before list_add_tail? It doesn't make sense to initialize the list before checking call_controls_obsolete. Maybe this suggestion should go in a different patch. -- Asier Gutierrez Huawei