netdev - [PATCH v2] net: ipv4: fix clang -Wformat warnings

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Message-Id: <20220709003704.646568-1-justinstitt@google.com>
Date:   Fri,  8 Jul 2022 17:37:04 -0700
From:   Justin Stitt <justinstitt@...gle.com>
To:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S . Miller" <davem@...emloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>
Cc:     Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
        Justin Stitt <justinstitt@...gle.com>,
        Joe Perches <joe@...ches.com>
Subject: [PATCH v2] net: ipv4: fix clang -Wformat warnings

When building with Clang we encounter these warnings:
| net/ipv4/ah4.c:513:4: error: format specifies type 'unsigned short' but
| the argument has type 'int' [-Werror,-Wformat]
| aalg_desc->uinfo.auth.icv_fullbits / 8);
-
| net/ipv4/esp4.c:1114:5: error: format specifies type 'unsigned short'
| but the argument has type 'int' [-Werror,-Wformat]
| aalg_desc->uinfo.auth.icv_fullbits / 8);

`aalg_desc->uinfo.auth.icv_fullbits` is a u16 but due to default
argument promotion becomes an int.

Variadic functions (printf-like) undergo default argument promotion.
Documentation/core-api/printk-formats.rst specifically recommends using
the promoted-to-type's format flag.

As per C11 6.3.1.1:
(https://www.open-std.org/jtc1/sc22/wg14/www/docs/n1548.pdf) `If an int
can represent all values of the original type ..., the value is
converted to an int; otherwise, it is converted to an unsigned int.
These are called the integer promotions.` Thus it makes sense to change
%hu to %d not only to follow this standard but to suppress the warning
as well.

Link: https://github.com/ClangBuiltLinux/linux/issues/378
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
Suggested-by: Joe Perches <joe@...ches.com>
Suggested-by: Nathan Chancellor <nathan@...nel.org>
Suggested-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
diff from v1 -> v2:
* packaged two related patches together: (Suggested by Nick)
  - https://lore.kernel.org/all/20220707181532.762452-1-justinstitt@google.com/
  - https://lore.kernel.org/all/20220707173040.704116-1-justinstitt@google.com/
* use Joe's suggestion regarding `%u` over `%d`.

 net/ipv4/ah4.c  | 2 +-
 net/ipv4/esp4.c | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/ah4.c b/net/ipv4/ah4.c
index 6eea1e9e998d..f8ad04470d3a 100644
--- a/net/ipv4/ah4.c
+++ b/net/ipv4/ah4.c
@@ -507,7 +507,7 @@ static int ah_init_state(struct xfrm_state *x)
 
 	if (aalg_desc->uinfo.auth.icv_fullbits/8 !=
 	    crypto_ahash_digestsize(ahash)) {
-		pr_info("%s: %s digestsize %u != %hu\n",
+		pr_info("%s: %s digestsize %u != %u\n",
 			__func__, x->aalg->alg_name,
 			crypto_ahash_digestsize(ahash),
 			aalg_desc->uinfo.auth.icv_fullbits / 8);
diff --git a/net/ipv4/esp4.c b/net/ipv4/esp4.c
index b21238df3301..b694f352ce7a 100644
--- a/net/ipv4/esp4.c
+++ b/net/ipv4/esp4.c
@@ -1108,7 +1108,7 @@ static int esp_init_authenc(struct xfrm_state *x)
 		err = -EINVAL;
 		if (aalg_desc->uinfo.auth.icv_fullbits / 8 !=
 		    crypto_aead_authsize(aead)) {
-			pr_info("ESP: %s digestsize %u != %hu\n",
+			pr_info("ESP: %s digestsize %u != %u\n",
 				x->aalg->alg_name,
 				crypto_aead_authsize(aead),
 				aalg_desc->uinfo.auth.icv_fullbits / 8);
-- 
2.37.0.rc0.161.g10f37bed90-goog