linux-kernel - Re: Clang warnings in net/phonet

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Date:   Sat, 26 Jan 2019 01:10:27 -0700
From:   Nathan Chancellor <natechancellor@...il.com>
To:     Rémi Denis-Courmont <remi@...lab.net>,
        Remi Denis-Courmont <courmisch@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Nick Desaulniers <ndesaulniers@...gle.com>
Subject: Re: Clang warnings in net/phonet

On Mon, Jan 07, 2019 at 07:54:20PM -0700, Nathan Chancellor wrote:
> Hi all,
> 
> When building the kernel with Clang, this warning comes up in net/phonet.
> 
> net/phonet/pep.c:224:16: warning: array index 1 is past the end of the array (which contains 1 element) [-Warray-bounds]
>         ph->data[0] = oph->data[1]; /* CTRL id */
>                       ^         ~
> include/net/phonet/pep.h:66:3: note: array 'data' declared here
>                 u8              data[1];
>                 ^
> net/phonet/pep.c:281:10: warning: array index 1 is past the end of the array (which contains 1 element) [-Warray-bounds]
>         switch (hdr->data[1]) {
>                 ^         ~
> include/net/phonet/pep.h:66:3: note: array 'data' declared here
>                 u8              data[1];
>                 ^
> net/phonet/pep.c:285:12: warning: array index 4 is past the end of the array (which contains 1 element) [-Warray-bounds]
>                         switch (hdr->data[4]) {
>                                 ^         ~
> include/net/phonet/pep.h:66:3: note: array 'data' declared here
>                 u8              data[1];
>                 ^
> net/phonet/pep.c:295:8: warning: array index 4 is past the end of the array (which contains 1 element) [-Warray-bounds]
>                         if (hdr->data[4] == PEP_IND_READY)
>                             ^         ~
> include/net/phonet/pep.h:66:3: note: array 'data' declared here
>                 u8              data[1];
>                 ^
> net/phonet/pep.c:304:21: warning: array index 4 is past the end of the array (which contains 1 element) [-Warray-bounds]
>                 atomic_add(wake = hdr->data[4], &pn->tx_credits);
>                                   ^         ~
> include/net/phonet/pep.h:66:3: note: array 'data' declared here
>                 u8              data[1];
>                 ^
> net/phonet/pep.c:509:9: warning: array index 4 is past the end of the array (which contains 1 element) [-Warray-bounds]
>         n_sb = hdr->data[4];
>                ^         ~
> include/net/phonet/pep.h:66:3: note: array 'data' declared here
>                 u8              data[1];
>                 ^
> net/phonet/pep.c:817:14: warning: array index 1 is past the end of the array (which contains 1 element) [-Warray-bounds]
>         peer_type = hdr->other_pep_type << 8;
>                     ^    ~~~~~~~~~~~~~~
> include/net/phonet/pep.h:66:3: note: array 'data' declared here
>                 u8              data[1];
>                 ^
> net/phonet/pep.c:820:9: warning: array index 4 is past the end of the array (which contains 1 element) [-Warray-bounds]
>         n_sb = hdr->data[4];
>                ^         ~
> include/net/phonet/pep.h:66:3: note: array 'data' declared here
>                 u8              data[1];
>                 ^
> 8 warnings generated.
> 
> I have taken a look at the effected code but I can't really figure out
> the proper fix for this warning (my knowledge of C just isn't there
> yet). Nick had suggested changing 'u8 data[1]' to 'u8 *data' in
> 'struct pnpipehdr', which seems logical but I can't say for sure. Any
> advice would be appreciated :)
> 
> Thanks,
> Nathan

Gentle ping?