From: Larry Finger Date: Fri, 4 Nov 2022 01:27:50 +0000 (-0500) Subject: staging: rtl8192e: Fix divide fault when calculating beacon age X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=bb5b5e2104ca000888df89e35ff42c677df22671;p=linux.git staging: rtl8192e: Fix divide fault when calculating beacon age When the configuration parameter CONFIG_HZ is less that 100, the compiler generates an error as follows: ../drivers/staging/rtl8192e/rtllib_wx.c: In function 'rtl819x_translate_scan': ../drivers/staging/rtl8192e/rtllib_wx.c:220:57: warning: division by zero [-Wdiv-by-zero] 220 | (jiffies - network->last_scanned) / (HZ / 100)); | ^ In file included from ../include/linux/skbuff.h:45, from ../include/linux/if_ether.h:19, from ../include/linux/etherdevice.h:20, from ../drivers/staging/rtl8192e/rtllib_wx.c:18: ../drivers/staging/rtl8192e/rtllib_wx.c: In function 'rtllib_wx_get_scan': ../drivers/staging/rtl8192e/rtllib_wx.c:261:70: warning: division by zero [-Wdiv-by-zero] 261 | (jiffies - network->last_scanned) / | In fact, is HZ is not a multiple of 100, the calculation will be wrong, but it will compile correctly. The fix is to get rid of the (HZ / 100) portion. To decrease any round-off errors, the compiler is forced to perform the 100 * jiffies-difference before dividing by HZ. This patch is only compile tested. Reported-by: Randy Dunlap Acked-by: Randy Dunlap # build-tested Signed-off-by: Larry Finger Tested-by: Philipp Hortmann Link: https://lore.kernel.org/r/20221104012750.2076-1-Larry.Finger@lwfinger.net Signed-off-by: Greg Kroah-Hartman --- diff --git a/drivers/staging/rtl8192e/rtllib_wx.c b/drivers/staging/rtl8192e/rtllib_wx.c index da2c41c9b92f1..217426ee2e92a 100644 --- a/drivers/staging/rtl8192e/rtllib_wx.c +++ b/drivers/staging/rtl8192e/rtllib_wx.c @@ -217,7 +217,7 @@ static inline char *rtl819x_translate_scan(struct rtllib_device *ieee, p = custom; p += scnprintf(p, MAX_CUSTOM_LEN - (p - custom), " Last beacon: %lums ago", - (jiffies - network->last_scanned) / (HZ / 100)); + (100 * (jiffies - network->last_scanned)) / HZ); iwe.u.data.length = p - custom; if (iwe.u.data.length) start = iwe_stream_add_point_rsl(info, start, stop, @@ -258,8 +258,8 @@ int rtllib_wx_get_scan(struct rtllib_device *ieee, escape_essid(network->ssid, network->ssid_len), network->bssid, - (jiffies - network->last_scanned) / - (HZ / 100)); + (100 * (jiffies - network->last_scanned)) / + HZ); } spin_unlock_irqrestore(&ieee->lock, flags);