linux-hardening - [PATCH] ARM: Replace all non-returning strlcpy with strscpy

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Date:   Tue, 30 May 2023 15:55:01 +0000
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     Russell King <linux@...linux.org.uk>
Cc:     linux-hardening@...r.kernel.org,
        Azeem Shaikh <azeemshaikh38@...il.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        "Russell King (Oracle)" <rmk+kernel@...linux.org.uk>,
        Linus Walleij <linus.walleij@...aro.org>,
        Amit Daniel Kachhap <amit.kachhap@....com>,
        Ard Biesheuvel <ardb@...nel.org>
Subject: [PATCH] ARM: Replace all non-returning strlcpy with strscpy

strlcpy() reads the entire source buffer first.
This read may exceed the destination size limit.
This is both inefficient and can lead to linear read
overflows if a source string is not NUL-terminated [1].
In an effort to remove strlcpy() completely [2], replace
strlcpy() here with strscpy().
No return values were used, so direct replacement is safe.

[1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
[2] https://github.com/KSPP/linux/issues/89

Signed-off-by: Azeem Shaikh <azeemshaikh38@...il.com>
---
 arch/arm/kernel/atags_parse.c |    4 ++--
 arch/arm/kernel/setup.c       |    2 +-
 arch/arm/kernel/vdso.c        |    2 +-
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/arch/arm/kernel/atags_parse.c b/arch/arm/kernel/atags_parse.c
index 373b61f9a4f0..33f6eb5213a5 100644
--- a/arch/arm/kernel/atags_parse.c
+++ b/arch/arm/kernel/atags_parse.c
@@ -127,7 +127,7 @@ static int __init parse_tag_cmdline(const struct tag *tag)
 #elif defined(CONFIG_CMDLINE_FORCE)
 	pr_warn("Ignoring tag cmdline (using the default kernel command line)\n");
 #else
-	strlcpy(default_command_line, tag->u.cmdline.cmdline,
+	strscpy(default_command_line, tag->u.cmdline.cmdline,
 		COMMAND_LINE_SIZE);
 #endif
 	return 0;
@@ -224,7 +224,7 @@ setup_machine_tags(void *atags_vaddr, unsigned int machine_nr)
 	}
 
 	/* parse_early_param needs a boot_command_line */
-	strlcpy(boot_command_line, from, COMMAND_LINE_SIZE);
+	strscpy(boot_command_line, from, COMMAND_LINE_SIZE);
 
 	return mdesc;
 }
diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c
index 75cd4699e7b3..3048a685ea79 100644
--- a/arch/arm/kernel/setup.c
+++ b/arch/arm/kernel/setup.c
@@ -1142,7 +1142,7 @@ void __init setup_arch(char **cmdline_p)
 	setup_initial_init_mm(_text, _etext, _edata, _end);
 
 	/* populate cmd_line too for later use, preserving boot_command_line */
-	strlcpy(cmd_line, boot_command_line, COMMAND_LINE_SIZE);
+	strscpy(cmd_line, boot_command_line, COMMAND_LINE_SIZE);
 	*cmdline_p = cmd_line;
 
 	early_fixmap_init();
diff --git a/arch/arm/kernel/vdso.c b/arch/arm/kernel/vdso.c
index 3408269d19c7..f297d66a8a76 100644
--- a/arch/arm/kernel/vdso.c
+++ b/arch/arm/kernel/vdso.c
@@ -135,7 +135,7 @@ static Elf32_Sym * __init find_symbol(struct elfinfo *lib, const char *symname)
 
 		if (lib->dynsym[i].st_name == 0)
 			continue;
-		strlcpy(name, lib->dynstr + lib->dynsym[i].st_name,
+		strscpy(name, lib->dynstr + lib->dynsym[i].st_name,
 			MAX_SYMNAME);
 		c = strchr(name, '@');
 		if (c)