netdev - Re: [PATCH] net: Fix for_each_netdev

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Date:   Sat, 16 Feb 2019 13:01:28 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>, hauke.mehrtens@...el.com
Cc:     netdev@...r.kernel.org, jarod@...hat.com, hauke@...ke-m.de,
        stable@...r.kernel.org
Subject: Re: [PATCH] net: Fix for_each_netdev_feature on Big endian



On 02/15/2019 08:24 PM, David Miller wrote:
> From: Hauke Mehrtens <hauke.mehrtens@...el.com>
> Date: Fri, 15 Feb 2019 17:58:54 +0100
> 
>> The features attribute is of type u64 and stored in the native endianes on
>> the system. The for_each_set_bit() macro takes a pointer to a 32 bit array
>> and goes over the bits in this area. On little Endian systems this also
>> works with an u64 as the most significant bit is on the highest address,
>> but on big endian the words are swapped. When we expect bit 15 here we get
>> bit 47 (15 + 32).
>>
>> This patch converts it more or less to its own for_each_set_bit()
>> implementation which works on 64 bit integers directly. This is then
>> completely in host endianness and should work like expected.
>>
>> Fixes: fd867d51f ("net/core: generic support for disabling netdev features down stack")
>> Cc: stable@...r.kernel.org
>> Signed-off-by: Hauke Mehrtens <hauke.mehrtens@...el.com>
> 
> Applied and queued up for -stable.
> 
> Please do not CC: stable for networking fixes, I handle -stable submissions
> myself manually and this is documented in the netdev FAQ.
> 

This commit added a call to fls64(), but not the needed include.

This might break some uses I think.

I suggest the following fix :

diff --git a/include/linux/netdev_features.h b/include/linux/netdev_features.h
index c50cedb65cf56fe7d722a5a321b714ed83f449a0..d3f61011f4346e4ea80b61f88bd24541dd006014 100644
--- a/include/linux/netdev_features.h
+++ b/include/linux/netdev_features.h
@@ -11,6 +11,7 @@
 #define _LINUX_NETDEV_FEATURES_H
 
 #include <linux/types.h>
+#include <linux/bitops.h>
 #include <asm/byteorder.h>
 
 typedef u64 netdev_features_t;