[v2] tracing/boot: Replace strlcpy with strscpy

[PATCH v2] tracing/boot: Replace strlcpy with strscpy

Posted by Azeem Shaikh 2 years, 7 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().

Direct replacement is safe here since return value of -errno
is used to check for truncation instead of sizeof(dest).

[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>
---
v2:
 * Use "< 0" instead of -E2BIG.

v1:
 * https://lore.kernel.org/all/20230613004125.3539934-1-azeemshaikh38@gmail.com/

 kernel/trace/trace_boot.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
index 778200dd8ede..7ccc7a8e155b 100644
--- a/kernel/trace/trace_boot.c
+++ b/kernel/trace/trace_boot.c
@@ -31,7 +31,7 @@ trace_boot_set_instance_options(struct trace_array *tr, struct xbc_node *node)
 
 	/* Common ftrace options */
 	xbc_node_for_each_array_value(node, "options", anode, p) {
-		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) {
+		if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0) {
 			pr_err("String is too long: %s\n", p);
 			continue;
 		}
@@ -87,7 +87,7 @@ trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node)
 	const char *p;
 
 	xbc_node_for_each_array_value(node, "events", anode, p) {
-		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) {
+		if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0) {
 			pr_err("String is too long: %s\n", p);
 			continue;
 		}
@@ -486,7 +486,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
 
 	p = xbc_node_find_value(enode, "filter", NULL);
 	if (p && *p != '\0') {
-		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf))
+		if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0)
 			pr_err("filter string is too long: %s\n", p);
 		else if (apply_event_filter(file, buf) < 0)
 			pr_err("Failed to apply filter: %s\n", buf);
@@ -494,7 +494,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
 
 	if (IS_ENABLED(CONFIG_HIST_TRIGGERS)) {
 		xbc_node_for_each_array_value(enode, "actions", anode, p) {
-			if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf))
+			if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0)
 				pr_err("action string is too long: %s\n", p);
 			else if (trigger_process_regex(file, buf) < 0)
 				pr_err("Failed to apply an action: %s\n", p);
-- 
2.41.0.162.gfafddb0af9-goog

Re: [PATCH v2] tracing/boot: Replace strlcpy with strscpy

Posted by Kees Cook 2 years, 7 months ago

On Thu, 15 Jun 2023 18:04:20 +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().
> 
> [...]

Applied to for-next/hardening, thanks!

[1/1] tracing/boot: Replace strlcpy with strscpy
      https://git.kernel.org/kees/c/b1c38314f756

-- 
Kees Cook

Re: [PATCH v2] tracing/boot: Replace strlcpy with strscpy

Posted by Steven Rostedt 2 years, 7 months ago

On Tue, 20 Jun 2023 13:28:26 -0700
Kees Cook <keescook@chromium.org> wrote:

> On Thu, 15 Jun 2023 18:04:20 +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().
> > 
> > [...]  
> 
> Applied to for-next/hardening, thanks!
> 
> [1/1] tracing/boot: Replace strlcpy with strscpy
>       https://git.kernel.org/kees/c/b1c38314f756
> 

I was going to add this to my queue.

-- Steve

Re: [PATCH v2] tracing/boot: Replace strlcpy with strscpy

Posted by Kees Cook 2 years, 7 months ago

On Tue, Jun 20, 2023 at 04:33:25PM -0400, Steven Rostedt wrote:
> On Tue, 20 Jun 2023 13:28:26 -0700
> Kees Cook <keescook@chromium.org> wrote:
> 
> > On Thu, 15 Jun 2023 18:04:20 +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().
> > > 
> > > [...]  
> > 
> > Applied to for-next/hardening, thanks!
> > 
> > [1/1] tracing/boot: Replace strlcpy with strscpy
> >       https://git.kernel.org/kees/c/b1c38314f756
> > 
> 
> I was going to add this to my queue.

Ah, okay, no worries. I will drop it from mine.

-- 
Kees Cook

Re: [PATCH v2] tracing/boot: Replace strlcpy with strscpy

Posted by Steven Rostedt 2 years, 7 months ago

On Tue, 20 Jun 2023 13:35:14 -0700
Kees Cook <keescook@chromium.org> wrote:

> > > Applied to for-next/hardening, thanks!
> > > 
> > > [1/1] tracing/boot: Replace strlcpy with strscpy
> > >       https://git.kernel.org/kees/c/b1c38314f756
> > >   
> > 
> > I was going to add this to my queue.  
> 
> Ah, okay, no worries. I will drop it from mine.

Maybe I should have let you take it. I had v1 in my queue, and pushed
that one :-p

I'll fix it later.

Thanks,

-- Steve

Re: [PATCH v2] tracing/boot: Replace strlcpy with strscpy

Posted by Masami Hiramatsu (Google) 2 years, 7 months ago

On Thu, 15 Jun 2023 18:04:20 +0000
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().
> 
> Direct replacement is safe here since return value of -errno
> is used to check for truncation instead of sizeof(dest).
> 
> [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#strlcpy
> [2] https://github.com/KSPP/linux/issues/89
> 

Looks good to me.

Acked-by: Masami Hiramatsu (Google) <mhiramat@kernel.org>

Thanks!

> Signed-off-by: Azeem Shaikh <azeemshaikh38@gmail.com>
> ---
> v2:
>  * Use "< 0" instead of -E2BIG.
> 
> v1:
>  * https://lore.kernel.org/all/20230613004125.3539934-1-azeemshaikh38@gmail.com/
> 
>  kernel/trace/trace_boot.c |    8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/trace/trace_boot.c b/kernel/trace/trace_boot.c
> index 778200dd8ede..7ccc7a8e155b 100644
> --- a/kernel/trace/trace_boot.c
> +++ b/kernel/trace/trace_boot.c
> @@ -31,7 +31,7 @@ trace_boot_set_instance_options(struct trace_array *tr, struct xbc_node *node)
>  
>  	/* Common ftrace options */
>  	xbc_node_for_each_array_value(node, "options", anode, p) {
> -		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) {
> +		if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0) {
>  			pr_err("String is too long: %s\n", p);
>  			continue;
>  		}
> @@ -87,7 +87,7 @@ trace_boot_enable_events(struct trace_array *tr, struct xbc_node *node)
>  	const char *p;
>  
>  	xbc_node_for_each_array_value(node, "events", anode, p) {
> -		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf)) {
> +		if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0) {
>  			pr_err("String is too long: %s\n", p);
>  			continue;
>  		}
> @@ -486,7 +486,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
>  
>  	p = xbc_node_find_value(enode, "filter", NULL);
>  	if (p && *p != '\0') {
> -		if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf))
> +		if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0)
>  			pr_err("filter string is too long: %s\n", p);
>  		else if (apply_event_filter(file, buf) < 0)
>  			pr_err("Failed to apply filter: %s\n", buf);
> @@ -494,7 +494,7 @@ trace_boot_init_one_event(struct trace_array *tr, struct xbc_node *gnode,
>  
>  	if (IS_ENABLED(CONFIG_HIST_TRIGGERS)) {
>  		xbc_node_for_each_array_value(enode, "actions", anode, p) {
> -			if (strlcpy(buf, p, ARRAY_SIZE(buf)) >= ARRAY_SIZE(buf))
> +			if (strscpy(buf, p, ARRAY_SIZE(buf)) < 0)
>  				pr_err("action string is too long: %s\n", p);
>  			else if (trigger_process_regex(file, buf) < 0)
>  				pr_err("Failed to apply an action: %s\n", p);
> -- 
> 2.41.0.162.gfafddb0af9-goog
> 
> 


-- 
Masami Hiramatsu (Google) <mhiramat@kernel.org>