linux-hardening - [PATCH] Bluetooth: vhci: Avoid needless snprintf() calls

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Message-Id: <20250415161518.work.889-kees@kernel.org>
Date: Tue, 15 Apr 2025 09:15:19 -0700
From: Kees Cook <kees@...nel.org>
To: stable@...r.kernel.org
Cc: Kees Cook <kees@...nel.org>,
	kernel test robot <lkp@...el.com>,
	Marcel Holtmann <marcel@...tmann.org>,
	Luiz Augusto von Dentz <luiz.dentz@...il.com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-bluetooth@...r.kernel.org,
	Bill Wendling <morbo@...gle.com>,
	Justin Stitt <justinstitt@...gle.com>,
	Manish Mandlik <mmandlik@...gle.com>,
	linux-kernel@...r.kernel.org,
	llvm@...ts.linux.dev,
	linux-hardening@...r.kernel.org
Subject: [PATCH] Bluetooth: vhci: Avoid needless snprintf() calls

Avoid double-copying of string literals. Use a "const char *" for each
string instead of copying from .rodata into stack and then into the skb.
We can go directly from .rodata to the skb.

This also works around a Clang bug (that has since been fixed[1]).

Reported-by: kernel test robot <lkp@...el.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202401250927.1poZERd6-lkp@intel.com/
Fixes: ab4e4380d4e1 ("Bluetooth: Add vhci devcoredump support")
Link: https://github.com/llvm/llvm-project/commit/ea2e66aa8b6e363b89df66dc44275a0d7ecd70ce [1]
Cc: stable@...r.kernel.org
Signed-off-by: Kees Cook <kees@...nel.org>
---
Cc: Marcel Holtmann <marcel@...tmann.org>
Cc: Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc: Josh Poimboeuf <jpoimboe@...nel.org>
Cc: Nathan Chancellor <nathan@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: linux-bluetooth@...r.kernel.org
---
 drivers/bluetooth/hci_vhci.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/drivers/bluetooth/hci_vhci.c b/drivers/bluetooth/hci_vhci.c
index 7651321d351c..9ac22e4a070b 100644
--- a/drivers/bluetooth/hci_vhci.c
+++ b/drivers/bluetooth/hci_vhci.c
@@ -289,18 +289,18 @@ static void vhci_coredump(struct hci_dev *hdev)
 
 static void vhci_coredump_hdr(struct hci_dev *hdev, struct sk_buff *skb)
 {
-	char buf[80];
+	const char *buf;
 
-	snprintf(buf, sizeof(buf), "Controller Name: vhci_ctrl\n");
+	buf = "Controller Name: vhci_ctrl\n";
 	skb_put_data(skb, buf, strlen(buf));
 
-	snprintf(buf, sizeof(buf), "Firmware Version: vhci_fw\n");
+	buf = "Firmware Version: vhci_fw\n";
 	skb_put_data(skb, buf, strlen(buf));
 
-	snprintf(buf, sizeof(buf), "Driver: vhci_drv\n");
+	buf = "Driver: vhci_drv\n";
 	skb_put_data(skb, buf, strlen(buf));
 
-	snprintf(buf, sizeof(buf), "Vendor: vhci\n");
+	buf = "Vendor: vhci\n";
 	skb_put_data(skb, buf, strlen(buf));
 }
 
-- 
2.34.1