linux-kernel - [PATCH] l2tp: l2tp_debugfs: fix Clang -Wformat warnings

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Date:   Thu,  7 Jul 2022 15:14:56 -0700
From:   Justin Stitt <justinstitt@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>,
        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>, Tom Parkin <tparkin@...alix.com>,
        Justin Stitt <justinstitt@...gle.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, llvm@...ts.linux.dev
Subject: [PATCH] l2tp: l2tp_debugfs: fix Clang -Wformat warnings

When building with Clang we encounter the following warnings:
| net/l2tp/l2tp_debugfs.c:187:40: error: format specifies type 'unsigned
| short' but the argument has type 'u32' (aka 'unsigned int')
| [-Werror,-Wformat] seq_printf(m, "   nr %hu, ns %hu\n", session->nr,
| session->ns);
-
| net/l2tp/l2tp_debugfs.c:196:32: error: format specifies type 'unsigned
| short' but the argument has type 'int' [-Werror,-Wformat]
| session->l2specific_type, l2tp_get_l2specific_len(session));
-
| net/l2tp/l2tp_debugfs.c:219:6: error: format specifies type 'unsigned
| short' but the argument has type 'u32' (aka 'unsigned int')
| [-Werror,-Wformat] session->nr, session->ns,

Both session->nr and ->nc are of type `u32`. The currently used format
specifier is `%hu` which describes a `u16`. My proposed fix is to listen
to Clang and use the correct format specifier `%u`.

For the warning at line 196, l2tp_get_l2specific_len() returns an int
and should therefore be using the `%d` format specifier.

Link: https://github.com/ClangBuiltLinux/linux/issues/378
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Related l2tp -Wformat patch:
https://lore.kernel.org/all/20220706230833.535238-1-justinstitt@google.com/

 net/l2tp/l2tp_debugfs.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/l2tp/l2tp_debugfs.c b/net/l2tp/l2tp_debugfs.c
index 9d1aafe75f92..4595b56d175d 100644
--- a/net/l2tp/l2tp_debugfs.c
+++ b/net/l2tp/l2tp_debugfs.c
@@ -184,7 +184,7 @@ static void l2tp_dfs_seq_session_show(struct seq_file *m, void *v)
 		   session->pwtype == L2TP_PWTYPE_PPP ? "PPP" :
 		   "");
 	if (session->send_seq || session->recv_seq)
-		seq_printf(m, "   nr %hu, ns %hu\n", session->nr, session->ns);
+		seq_printf(m, "   nr %u, ns %u\n", session->nr, session->ns);
 	seq_printf(m, "   refcnt %d\n", refcount_read(&session->ref_count));
 	seq_printf(m, "   config 0/0/%c/%c/-/%s %08x %u\n",
 		   session->recv_seq ? 'R' : '-',
@@ -192,7 +192,7 @@ static void l2tp_dfs_seq_session_show(struct seq_file *m, void *v)
 		   session->lns_mode ? "LNS" : "LAC",
 		   0,
 		   jiffies_to_msecs(session->reorder_timeout));
-	seq_printf(m, "   offset 0 l2specific %hu/%hu\n",
+	seq_printf(m, "   offset 0 l2specific %hu/%d\n",
 		   session->l2specific_type, l2tp_get_l2specific_len(session));
 	if (session->cookie_len) {
 		seq_printf(m, "   cookie %02x%02x%02x%02x",
@@ -215,7 +215,7 @@ static void l2tp_dfs_seq_session_show(struct seq_file *m, void *v)
 		seq_puts(m, "\n");
 	}
 
-	seq_printf(m, "   %hu/%hu tx %ld/%ld/%ld rx %ld/%ld/%ld\n",
+	seq_printf(m, "   %u/%u tx %ld/%ld/%ld rx %ld/%ld/%ld\n",
 		   session->nr, session->ns,
 		   atomic_long_read(&session->stats.tx_packets),
 		   atomic_long_read(&session->stats.tx_bytes),
-- 
2.37.0.rc0.161.g10f37bed90-goog