[PATCH] netfilter: nft_bitwise: Adjust parentheses to fix memcmp size argument

[PATCH] netfilter: nft_bitwise: Adjust parentheses to fix memcmp size argument

[Nathan Chancellor]

clang warns:

net/netfilter/nft_bitwise.c:138:50: error: size argument in 'memcmp'
call is a comparison [-Werror,-Wmemsize-comparison]
        if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
                                      ~~~~~~~~~~~~~~~~~~^~
net/netfilter/nft_bitwise.c:138:6: note: did you mean to compare the
result of 'memcmp' instead?
        if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
            ^
                                                       )
net/netfilter/nft_bitwise.c:138:32: note: explicitly cast the argument
to size_t to silence this warning
        if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
                                      ^
                                      (size_t)(
1 error generated.

Adjust the parentheses so that the result of the sizeof is used for the
size argument in memcmp, rather than the result of the comparison (which
would always be true because sizeof is a non-zero number).

Fixes: bd8699e9e292 ("netfilter: nft_bitwise: add offload support")
Link: https://github.com/ClangBuiltLinux/linux/issues/638
Reported-by: kbuild test robot <lkp@intel.com>
Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
---
 net/netfilter/nft_bitwise.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/netfilter/nft_bitwise.c b/net/netfilter/nft_bitwise.c
index 1f04ed5c518c..974300178fa9 100644
--- a/net/netfilter/nft_bitwise.c
+++ b/net/netfilter/nft_bitwise.c
@@ -135,8 +135,8 @@ static int nft_bitwise_offload(struct nft_offload_ctx *ctx,
 {
 	const struct nft_bitwise *priv = nft_expr_priv(expr);
 
-	if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
-	    priv->sreg != priv->dreg))
+	if (memcmp(&priv->xor, &zero, sizeof(priv->xor)) ||
+	    priv->sreg != priv->dreg)
 		return -EOPNOTSUPP;
 
 	memcpy(&ctx->regs[priv->dreg].mask, &priv->mask, sizeof(priv->mask));
-- 
2.23.0.rc2

Re: [PATCH] netfilter: nft_bitwise: Adjust parentheses to fix memcmp size argument

[Nick Desaulniers]

On Wed, Aug 14, 2019 at 9:58 AM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> clang warns:
>
> net/netfilter/nft_bitwise.c:138:50: error: size argument in 'memcmp'
> call is a comparison [-Werror,-Wmemsize-comparison]
>         if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
>                                       ~~~~~~~~~~~~~~~~~~^~
> net/netfilter/nft_bitwise.c:138:6: note: did you mean to compare the
> result of 'memcmp' instead?
>         if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
>             ^
>                                                        )
> net/netfilter/nft_bitwise.c:138:32: note: explicitly cast the argument
> to size_t to silence this warning
>         if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
>                                       ^
>                                       (size_t)(
> 1 error generated.
>
> Adjust the parentheses so that the result of the sizeof is used for the
> size argument in memcmp, rather than the result of the comparison (which
> would always be true because sizeof is a non-zero number).
>
> Fixes: bd8699e9e292 ("netfilter: nft_bitwise: add offload support")
> Link: https://github.com/ClangBuiltLinux/linux/issues/638
> Reported-by: kbuild test robot <lkp@intel.com>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>

oh no! thanks for the patch.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  net/netfilter/nft_bitwise.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/netfilter/nft_bitwise.c b/net/netfilter/nft_bitwise.c
> index 1f04ed5c518c..974300178fa9 100644
> --- a/net/netfilter/nft_bitwise.c
> +++ b/net/netfilter/nft_bitwise.c
> @@ -135,8 +135,8 @@ static int nft_bitwise_offload(struct nft_offload_ctx *ctx,
>  {
>         const struct nft_bitwise *priv = nft_expr_priv(expr);
>
> -       if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
> -           priv->sreg != priv->dreg))
> +       if (memcmp(&priv->xor, &zero, sizeof(priv->xor)) ||
> +           priv->sreg != priv->dreg)
>                 return -EOPNOTSUPP;
>
>         memcpy(&ctx->regs[priv->dreg].mask, &priv->mask, sizeof(priv->mask));
> --
> 2.23.0.rc2
>

-- 
Thanks,
~Nick Desaulniers

Re: [PATCH] netfilter: nft_bitwise: Adjust parentheses to fix memcmp size argument

[Pablo Neira Ayuso]

On Wed, Aug 14, 2019 at 09:58:09AM -0700, Nathan Chancellor wrote:
> clang warns:
> 
> net/netfilter/nft_bitwise.c:138:50: error: size argument in 'memcmp'
> call is a comparison [-Werror,-Wmemsize-comparison]
>         if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
>                                       ~~~~~~~~~~~~~~~~~~^~

Applied, thanks.

Re: [PATCH] netfilter: nft_bitwise: Adjust parentheses to fix memcmp size argument

[Joe Perches]

On Wed, 2019-08-14 at 09:58 -0700, Nathan Chancellor wrote:
> clang warns:
> 
> net/netfilter/nft_bitwise.c:138:50: error: size argument in 'memcmp'
> call is a comparison [-Werror,-Wmemsize-comparison]
>         if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
>                                       ~~~~~~~~~~~~~~~~~~^~
> net/netfilter/nft_bitwise.c:138:6: note: did you mean to compare the
> result of 'memcmp' instead?
>         if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
>             ^
>                                                        )
> net/netfilter/nft_bitwise.c:138:32: note: explicitly cast the argument
> to size_t to silence this warning
>         if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
>                                       ^
>                                       (size_t)(
> 1 error generated.
> 
> Adjust the parentheses so that the result of the sizeof is used for the
> size argument in memcmp, rather than the result of the comparison (which
> would always be true because sizeof is a non-zero number).
> 
> Fixes: bd8699e9e292 ("netfilter: nft_bitwise: add offload support")
> Link: https://github.com/ClangBuiltLinux/linux/issues/638
> Reported-by: kbuild test robot <lkp@intel.com>
> Signed-off-by: Nathan Chancellor <natechancellor@gmail.com>
> ---
>  net/netfilter/nft_bitwise.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/net/netfilter/nft_bitwise.c b/net/netfilter/nft_bitwise.c
[]
> @@ -135,8 +135,8 @@ static int nft_bitwise_offload(struct nft_offload_ctx *ctx,
>  {
>  	const struct nft_bitwise *priv = nft_expr_priv(expr);
>  
> -	if (memcmp(&priv->xor, &zero, sizeof(priv->xor) ||
> -	    priv->sreg != priv->dreg))
> +	if (memcmp(&priv->xor, &zero, sizeof(priv->xor)) ||
> +	    priv->sreg != priv->dreg)

This code should use memchr_inv and not compare against a
static uninitialized struct.

Perhaps linux should introduce and use memcchr like bsd. 
or just add something like #define memcchr memchr_inv