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staging: rtl8192e: Fix divide fault when calculating beacon age

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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 <rdunlap@infradead.org>
Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested
Signed-off-by: Larry Finger <Larry.Finger@lwfinger.net>
Tested-by: Philipp Hortmann <philipp.g.hortmann@gmail.com>
Link: https://lore.kernel.org/r/20221104012750.2076-1-Larry.Finger@lwfinger.net
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Larry Finger
2022-11-03 20:27:50 -05:00
committed by Greg Kroah-Hartman
parent dcb18f5140
commit bb5b5e2104
1 changed files with 3 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/staging/rtl8192e/rtllib_wx.c
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@@ -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);