Re: [PATCH] infiniband: avoid overflow warning

From	Arnd Bergmann <arnd@arndb.de>
Newsgroups	linux.kernel
Subject	Re: [PATCH] infiniband: avoid overflow warning
Date	2017-07-31 21:20 +0200
Message-ID	<u9ooq-1IS-13@gated-at.bofh.it> (permalink)
References	(1 earlier) <u9cZY-3eT-3@gated-at.bofh.it> <u9dsZ-3oE-5@gated-at.bofh.it> <u9kXx-7Zm-23@gated-at.bofh.it> <u9lqy-8oa-17@gated-at.bofh.it> <u9lAe-8rv-11@gated-at.bofh.it>
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On Mon, Jul 31, 2017 at 6:17 PM, Bart Van Assche <Bart.VanAssche@wdc.com> wrote:
> On Mon, 2017-07-31 at 18:04 +0200, Arnd Bergmann wrote:
>> On Mon, Jul 31, 2017 at 5:32 PM, Bart Van Assche <Bart.VanAssche@wdc.com> wrote:
>> > So inetaddr_event() assigns AF_INET so .sin_family and gcc warns about code
>> > that is only executed if .sin_family == AF_INET6? Since this warning is the
>> > result of incorrect interprocedural analysis by gcc, shouldn't this be
>> > reported as a bug to the gcc authors?
>>
>> I think the interprocedural analysis here is just a little worse than it could
>> be, but it's not actually correct.  It's not gcc that prints the warning (if
>> it did, then I'd agree it would be a gcc bug) but the warning is triggered
>> intentionally by the fortified version of memcpy in include/linux/string.h.
>>
>> The problem as I understand it is that gcc cannot guarantee that it
>> tracks the value of addr->sa_family at  least as far as the size of the
>> stack object, and it has no strict reason to do so, so the inlined
>> rdma_ip2gid() will still contain both cases.
>
> Hello Arnd,
>
> Had you already considered to uninline the rdma_ip2gid() function?

Not really, that would prevent the normal optimization from happening,
so that would be worse than uninlining addr_event() as I tried.

It would of course get rid of the warning, so if you think that's a better
solution, I won't complain.

       Arnd

Thread

[PATCH] infiniband: avoid overflow warning Arnd Bergmann <arnd@arndb.de> - 2017-07-31 09:00 +0200
  Re: [PATCH] infiniband: avoid overflow warning Moni Shoua <monis@mellanox.com> - 2017-07-31 09:10 +0200
    Re: [PATCH] infiniband: avoid overflow warning Arnd Bergmann <arnd@arndb.de> - 2017-07-31 09:40 +0200
      Re: [PATCH] infiniband: avoid overflow warning Bart Van Assche <Bart.VanAssche@wdc.com> - 2017-07-31 17:40 +0200
        Re: [PATCH] infiniband: avoid overflow warning Arnd Bergmann <arnd@arndb.de> - 2017-07-31 18:10 +0200
          Re: [PATCH] infiniband: avoid overflow warning Bart Van Assche <Bart.VanAssche@wdc.com> - 2017-07-31 18:20 +0200
            Re: [PATCH] infiniband: avoid overflow warning Arnd Bergmann <arnd@arndb.de> - 2017-07-31 21:20 +0200
              Re: [PATCH] infiniband: avoid overflow warning Daniel Micay <danielmicay@gmail.com> - 2017-07-31 21:40 +0200
      Re: [PATCH] infiniband: avoid overflow warning Kees Cook <keescook@chromium.org> - 2017-07-31 23:00 +0200
        Re: [PATCH] infiniband: avoid overflow warning Arnd Bergmann <arnd@arndb.de> - 2017-07-31 23:20 +0200
          Re: [PATCH] infiniband: avoid overflow warning Kees Cook <keescook@chromium.org> - 2017-07-31 23:20 +0200
            Re: [PATCH] infiniband: avoid overflow warning Daniel Micay <danielmicay@gmail.com> - 2017-07-31 23:40 +0200
            Re: [PATCH] infiniband: avoid overflow warning Arnd Bergmann <arnd@arndb.de> - 2017-08-01 00:00 +0200
              Re: [PATCH] infiniband: avoid overflow warning Kees Cook <keescook@chromium.org> - 2017-08-01 00:10 +0200

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