Re: [PATCH] infiniband: avoid overflow warning

From	Kees Cook <keescook@chromium.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH] infiniband: avoid overflow warning
Date	2017-07-31 23:00 +0200
Message-ID	<u9pXc-2wz-17@gated-at.bofh.it> (permalink)
References	<u9cQi-2Wn-9@gated-at.bofh.it> <u9cZY-3eT-3@gated-at.bofh.it> <u9dsZ-3oE-5@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Mon, Jul 31, 2017 at 12:30 AM, Arnd Bergmann <arnd@arndb.de> wrote:
> On Mon, Jul 31, 2017 at 9:08 AM, Moni Shoua <monis@mellanox.com> wrote:
>> On Mon, Jul 31, 2017 at 9:50 AM, Arnd Bergmann <arnd@arndb.de> wrote:
>>> --- a/include/rdma/ib_addr.h
>>> +++ b/include/rdma/ib_addr.h
>>> @@ -172,7 +172,8 @@ static inline int rdma_ip2gid(struct sockaddr *addr, union ib_gid *gid)
>>>                                        (struct in6_addr *)gid);
>>>                 break;
>>>         case AF_INET6:
>>> -               memcpy(gid->raw, &((struct sockaddr_in6 *)addr)->sin6_addr, 16);
>>> +               *(struct in6_addr *)&gid->raw =
>>> +                       ((struct sockaddr_in6 *)addr)->sin6_addr;

This seems reasonable.

>>>                 break;
>>>         default:
>>>                 return -EINVAL;
>> what happens if you replace 16 with sizeof(struct in6_addr)?
>
> Same thing: the problem is that gcc already knows the size of the structure we
> pass in here, and it is in fact shorter.

So gcc is ignoring both the cast (to 16 byte struct in6_addr) and the
caller's actual 128 byte struct sockaddr_storage, and looking only at
struct sockaddr? That seems really weird.

-Kees

-- 
Kees Cook
Pixel Security

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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