ARM: Replace all non-returning strlcpy with strscpy

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

Posted by Azeem Shaikh 2 years, 8 months ago

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@gmail.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)

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

Posted by Linus Walleij 2 years, 8 months ago

On Tue, May 30, 2023 at 5:55 PM Azeem Shaikh <azeemshaikh38@gmail.com> wrote:

> 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@gmail.com>

Reviewed-by: Linus Walleij <linus.walleij@linaro.org>

Please put this into Russell's patch tracker:
https://www.arm.linux.org.uk/developer/patches/

Yours,
Linus Walleij

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

Posted by Ard Biesheuvel 2 years, 8 months ago

On Wed, 31 May 2023 at 15:30, Linus Walleij <linus.walleij@linaro.org> wrote:
>
> On Tue, May 30, 2023 at 5:55 PM Azeem Shaikh <azeemshaikh38@gmail.com> wrote:
>
> > 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@gmail.com>
>
> Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
>
> Please put this into Russell's patch tracker:
> https://www.arm.linux.org.uk/developer/patches/
>

https://www.armlinux.org.uk/developer/patches/viewpatch.php?id=9300/1

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

Posted by Kees Cook 2 years, 8 months ago

On Tue, May 30, 2023 at 03:55:01PM +0000, Azeem Shaikh wrote:
> 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@gmail.com>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook