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b=OqawpK+/SGjuCXHUlp66L4kMt2l6aphRZIb86IfgL+Q4msKLilvBNA44o2k/R14wj QPOBjd5EpwRnZYYjwIkgckwuWRgjql6ZsYlQw4bqGCi/pAM21nPkHMrewRBGZGZ//2 C2mCimvMmGqENeI5QlbVAVYt6cYl1rRHr5mfNWTllBd6HOvnfGrhKuREe5gFygVUHE S/aFkpXGv2x0cXyNbHgxqynIvIYspwR9/PT2FyrAhzAESqwQxCY/ADxUQ5VXT35K4T 0BHvUi1e9QwUIrSWYAJOjrYOEth55ALeBDdEmPyK6pgv1ISanWHHS1UZTygtXgxnrI ZmmIW92P0D8DA== From: SeongJae Park To: SeongJae Park Cc: "# 6 . 16 . x" , Andrew Morton , damon@lists.linux.dev, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: (sashiko review) [RFC PATCH 1/2] mm/damon/core: validate damos_quota_goal->nid for node_mem_{used,free}_bp Date: Fri, 27 Mar 2026 19:29:55 -0700 Message-ID: <20260328022956.8415-1-sj@kernel.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260328005412.7606-2-sj@kernel.org> References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Rspamd-Queue-Id: B57641C0004 X-Stat-Signature: 6jsr4nkij4c5j4rrdbza94bc7jqmfshb X-Rspamd-Server: rspam06 X-HE-Tag: 1774664998-569559 X-HE-Meta: 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 vFMuRK9Z VfvtYJCT1tK6JvhBr6Dib5ALb8eFD01xN/feB0fxTVzpxlV7WIO6LEiHYS5be31MhbSMrBviq2q+81H8U8uZoiuTcIlD8ln0KulGPtAjdKGdjdJsiiyU7wd2h0D0gHMQkyyDLJXDolAO6Av0xq1MA4MX+hiCEzEYhITCJ0gcT9fj2GxZQeFdBegVNspP9sX4IR+pDHUwYGZgbNVW0mXjw/5Oh4OAqT/pNwfpqpWE2tqGY84S7Jif75aLBgP8/1VxR0ivlWNi8XxzWgkYLouztUx5tBT0gKHmClBxbxZDjthI53Fz254wiS95a4NYOYPGuQQI26Zqd/epnKgHaN2FESXjO53o4OyEOP91uR5DVuDtd/4Y= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Forwarding Sashiko review for doing discussions via mails. # review url: https://sashiko.dev/#/patchset/20260328005412.7606-2-sj@kernel.org # start of sashiko.dev inline review commit add63112781ae04626ae6cb9bce55a85234f6e49 Author: SeongJae Park mm/damon/core: validate damos_quota_goal->nid for node_mem_{used,free}_bp This commit adds validation for the given memory node id to prevent out of bounds access when calculating node memory metrics. If an invalid node id is provided, it defaults to returning 0% used or 100% free memory. > diff --git a/mm/damon/core.c b/mm/damon/core.c > --- a/mm/damon/core.c > +++ b/mm/damon/core.c [ ... ] > @@ -2239,12 +2239,24 @@ static inline u64 damos_get_some_mem_psi_total(void) > static __kernel_ulong_t damos_get_node_mem_bp( > struct damos_quota_goal *goal) > { > struct sysinfo i; > __kernel_ulong_t numerator; > > + if (invalid_mem_node(goal->nid)) { > + if (goal->metric == DAMOS_QUOTA_NODE_MEM_USED_BP) > + return 0; > + else /* DAMOS_QUOTA_NODE_MEM_FREE_BP */ > + return 10000; > + } > + > si_meminfo_node(&i, goal->nid); > if (goal->metric == DAMOS_QUOTA_NODE_MEM_USED_BP) > numerator = i.totalram - i.freeram; > else /* DAMOS_QUOTA_NODE_MEM_FREE_BP */ > numerator = i.freeram; > return mult_frac(numerator, 10000, i.totalram); Could this result in a division by zero panic? While invalid_mem_node() checks node_state(nid, N_MEMORY) to ensure the node has present memory pages, si_meminfo_node() sets i.totalram based solely on managed pages. If all memory on the node is reserved, i.totalram could be 0. Additionally, since the node_state() check is lockless, memory could be concurrently offlined after invalid_mem_node() but before si_meminfo_node(), also resulting in i.totalram being 0. Would it be safer to explicitly verify i.totalram is greater than 0 before calling mult_frac()? # end of sashiko.dev inline review # review url: https://sashiko.dev/#/patchset/20260328005412.7606-2-sj@kernel.org # # hkml [1] generated a draft of this mail. It can be regenerated # using below command: # # hkml patch sashiko_dev --for_forwarding \ # 20260328005412.7606-2-sj@kernel.org # # [1] https://github.com/sjp38/hackermail Sent using hkml (https://github.com/sjp38/hackermail)