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dkim=pass header.d=google.com header.s=20210112 header.b=dgpVaKng; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf14.hostedemail.com: domain of yuzhao@google.com designates 209.85.221.173 as permitted sender) smtp.mailfrom=yuzhao@google.com X-Stat-Signature: 15jdo654pgxuawm3q7jb4iej5r71h13d X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 0AAEF10011F X-HE-Tag: 1661186996-245849 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Aug 22, 2022 at 5:22 AM Dan Carpenter wrote: > > Hello Yu Zhao, > > The patch e02f70ddcaca: "mm: multi-gen LRU: debugfs interface" from > Aug 15, 2022, leads to the following Smatch static checker warning: > > mm/vmscan.c:5706 lru_gen_seq_write() > warn: uncapped user index 'cur[end]' > > mm/vmscan.c > 5654 static ssize_t lru_gen_seq_write(struct file *file, const char __user *src, > 5655 size_t len, loff_t *pos) ... > 5704 n = sscanf(cur, "%c %u %u %lu %n %u %n %lu %n", &cmd, &memcg_id, &nid, > 5705 &seq, &end, &swappiness, &end, &opt, &end); > --> 5706 if (n < 4 || cur[end]) { > ^^^^^^^^ > The static checker is correct that "end" comes from the user and it > can be any unsigned int. Thanks. No, %n is not a conversion -- sscanf() stores the number of chars consumed so far upon seeing it. What would be the recommended way to suppress this warning, if there is one? > This is debugfs code so there is no security > impact. > > 5707 err = -EINVAL; > 5708 break; > 5709 }