Joe Perches <joe@xxxxxxxxxxx> writes:
> On Wed, 2014-10-08 at 16:33 +0200, Jes Sorensen wrote:
>> Joe Perches <joe@xxxxxxxxxxx> writes:
>> > On Wed, 2014-10-08 at 15:46 +0300, Dan Carpenter wrote:
>> >> On Wed, Oct 08, 2014 at 05:26:11AM -0700, Joe Perches wrote:
>> >> > On Wed, 2014-10-08 at 13:40 +0300, Dan Carpenter wrote:
>> >> > > The return from myid() isn't aligned correctly for ether_addr_copy().
>> >> >
>> >> > Hey Dan.
>> >> >
>> >> > Actual evidence showing ether_addr_copy conversions
>> >> > may not always be wise.
>> >> >
>> >> > How did you find them?
>> >>
>> >> I was just trying to see how common these kinds of bugs are. It didn't
>> >> take long to find, but my impression is that they are rare and I got
>> >> lucky. These kinds of bugs are tricky to find and we don't have any
>> >> tools for it.
>> >
>> > As far as I know, that's true too.
>> >
>> > Jes, was the mac_addr field in this struct
>> > ever __aligned(2)?
>> >
>> > struct eeprom_priv {
>> > u8 bautoload_fail_flag;
>> > u8 bloadfile_fail_flag;
>> > u8 bloadmac_fail_flag;
>> > /* u8 bempty; */
>> > /* u8 sys_config; */
>> > u8 mac_addr[6]; /* PermanentAddress */
>> > ...
>> > }
>> >
>> > As far as I can tell from git history, it was
>> > that way at the first check-in.
>>
>> I may have removed other entries that were unused, and that caused it to
>> become mis-aligned. I can't say for sure - the fix is straight forward
>> though.
>
> One option is to add __aligned(2) to the mac_addr field
> and make no other change.
As I said in another mail, just move it to the front of the struct and
be done with it. No point in wasting alignment bytes if we don't have
to.
Jes
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