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bh=h72m34e8ACzA9A4ZDo6Vo+CVdwWYFX5qPSFc29TL/OI=; b=vpr0nWgDvrLsWXTdfsIATo5kBPnKdmS2CenSPVSxncc3zmDOL48DfP6UDQcaTQ332WqWaT 0Kt6w99qP6FzP9wnah46remCuCV3kcbNpyIv+/8dnhdsLiu8gpyflQhTXFCVzYvQxJgbXQ KTapFW83kv8Rr4VsaBQUsQdWKNEadf0= X-Rspam-User: Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=oracle.com header.s=corp-2022-7-12 header.b=qFWETsAc; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=Kj8ikU0J; dmarc=pass (policy=none) header.from=oracle.com; arc=pass ("microsoft.com:s=arcselector9901:i=1"); spf=pass (imf08.hostedemail.com: domain of dan.carpenter@oracle.com designates 205.220.177.32 as permitted sender) smtp.mailfrom=dan.carpenter@oracle.com X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 33E0F160029 X-Stat-Signature: rsuyeq5tswdzcz6abnb7ejcdb3pcs3ji X-HE-Tag: 1661236794-68770 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 10:49:20AM -0600, Yu Zhao wrote: > 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? Ah. Sorry! I didn't realize %n can be in the middle like that so Smatch only looks for %n at the end of the string. Easily fixed in Smatch. regards, dan carpenter