[ovs-dev] [patch_v2] build: Fix memset with zero size warning.

Eric Garver e at erig.me
Mon Mar 20 19:32:27 UTC 2017


On Mon, Mar 20, 2017 at 11:24:49AM -0700, Darrell Ball wrote:
> In file included from /usr/include/string.h:640:0,
>                   from ./lib/string.h:20,
>                   from /usr/include/netinet/icmp6.h:22,
>                   from ../lib/flow.h:21,
>                   from ../lib/flow.c:18:
> In function 'memset',
>      inlined from 'flow_push_vlan_uninit' at ../lib/flow.c:2188:19:
> /usr/include/x86_64-linux-gnu/bits/string3.h:81:30: error:
> call to '__warn_memset_zero_len' declared with attribute warning:
> memset used with constant zero length parameter; this could be
> due to transposed parameters [-Werror]
>         __warn_memset_zero_len ();
>                                ^
> cc1: all warnings being treated as errors
> make[2]: *** [lib/flow.lo] Error 1
> 
> At the same time, fix some similar bounds checks related to
> the same commit.
> 
> Signed-off-by: Darrell Ball <dlu998 at gmail.com>
> Fixes: f0fb825a3785 ("Add support for 802.1ad (QinQ tunneling)")
> CC: Eric Garver <e at erig.me>
> ---
> 
> v1->v2: Change some cosmetic bounds checks.
> 
>  lib/flow.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/lib/flow.c b/lib/flow.c
> index f628526..8e7d3ee 100644
> --- a/lib/flow.c
> +++ b/lib/flow.c
> @@ -2167,10 +2167,10 @@ void
>  flow_pop_vlan(struct flow *flow, struct flow_wildcards *wc)
>  {
>      int n = flow_count_vlan_headers(flow);
> -    if (n == 0) {
> +    if (n <= 0) {
>          return;
>      }
> -    if (wc) {
> +    if ((wc) && (n > 1)) {

This is redundant because of the if (n <= 0) return above, but it's
fine.

>          memset(&wc->masks.vlans[1], 0xff,
>                 sizeof(union flow_vlan_hdr) * (n - 1));
>      }
> @@ -2184,7 +2184,9 @@ flow_push_vlan_uninit(struct flow *flow, struct flow_wildcards *wc)
>  {
>      if (wc) {
>          int n = flow_count_vlan_headers(flow);
> -        memset(wc->masks.vlans, 0xff, sizeof(union flow_vlan_hdr) * n);
> +        if (n > 0) {
> +            memset(wc->masks.vlans, 0xff, sizeof(union flow_vlan_hdr) * n);
> +        }
>      }
>      memmove(&flow->vlans[1], &flow->vlans[0],
>              sizeof(union flow_vlan_hdr) * (FLOW_MAX_VLAN_HEADERS - 1));
> -- 
> 1.9.1
> 

Thanks for the clean up!

Acked-by: Eric Garver <e at erig.me>


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