linux-hardening - [PATCH v2] RISC-V: cpu: refactor deprecated strncpy

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Date:   Wed, 02 Aug 2023 00:21:58 +0000
From:   Justin Stitt <justinstitt@...gle.com>
To:     Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>
Cc:     linux-riscv@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Kees Cook <keescook@...omium.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        linux-hardening@...r.kernel.org,
        Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH v2] RISC-V: cpu: refactor deprecated strncpy

`strncpy` is deprecated for use on NUL-terminated destination strings [1].

Favor not copying strings onto stack and instead use strings directly.
This avoids hard-coding sizes and buffer lengths all together.

Link: https://github.com/KSPP/linux/issues/90
Cc: linux-hardening@...r.kernel.org
Suggested-by: Kees Cook <keescook@...omium.org>
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Changes in v2:
- Use strings directly instead of copying onto stack with `strscpy` (thanks Kees)
- Link to v1: https://lore.kernel.org/r/20230801-arch-riscv-kernel-v1-1-2b3f2dc0bc61@google.com
---
 arch/riscv/kernel/cpu.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/riscv/kernel/cpu.c b/arch/riscv/kernel/cpu.c
index a2fc952318e9..872fa7a47d68 100644
--- a/arch/riscv/kernel/cpu.c
+++ b/arch/riscv/kernel/cpu.c
@@ -271,21 +271,21 @@ static void print_isa(struct seq_file *f, const char *isa)
 
 static void print_mmu(struct seq_file *f)
 {
-	char sv_type[16];
+	const char *sv_type;
 
 #ifdef CONFIG_MMU
 #if defined(CONFIG_32BIT)
-	strncpy(sv_type, "sv32", 5);
+	sv_type = "sv32";
 #elif defined(CONFIG_64BIT)
 	if (pgtable_l5_enabled)
-		strncpy(sv_type, "sv57", 5);
+		sv_type = "sv57";
 	else if (pgtable_l4_enabled)
-		strncpy(sv_type, "sv48", 5);
+		sv_type = "sv48";
 	else
-		strncpy(sv_type, "sv39", 5);
+		sv_type = "sv39";
 #endif
 #else
-	strncpy(sv_type, "none", 5);
+	sv_type = "none";
 #endif /* CONFIG_MMU */
 	seq_printf(f, "mmu\t\t: %s\n", sv_type);
 }

---
base-commit: 5d0c230f1de8c7515b6567d9afba1f196fb4e2f4
change-id: 20230801-arch-riscv-kernel-14a048cc6467

Best regards,
--
Justin Stitt <justinstitt@...gle.com>