[PATCH RESEND] of: module: add buffer overflow check in of_modalias()

[PATCH RESEND] of: module: add buffer overflow check in of_modalias()

[Sergey Shtylyov]

In of_modalias(), if the buffer happens to be too small even for the 1st
snprintf() call, the len parameter will become negative and str parameter
(if not NULL initially) will point beyond the buffer's end. Add the buffer
overflow check after the 1st snprintf() call and fix such check after the
strlen() call (accounting for the terminating NUL char).

Fixes: bc575064d688 ("of/device: use of_property_for_each_string to parse compatible strings")
Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>

---
The patch is against the dt/linus branch of Rob Herring's linux.git repo...

 drivers/of/module.c |    7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

Index: linux/drivers/of/module.c
===================================================================
--- linux.orig/drivers/of/module.c
+++ linux/drivers/of/module.c
@@ -29,14 +29,15 @@ ssize_t of_modalias(const struct device_
 	csize = snprintf(str, len, "of:N%pOFn%c%s", np, 'T',
 			 of_node_get_device_type(np));
 	tsize = csize;
+	if (csize >= len)
+		csize = len > 0 ? len - 1 : 0;
 	len -= csize;
-	if (str)
-		str += csize;
+	str += csize;
 
 	of_property_for_each_string(np, "compatible", p, compat) {
 		csize = strlen(compat) + 1;
 		tsize += csize;
-		if (csize > len)
+		if (csize >= len)
 			continue;
 
 		csize = snprintf(str, len, "C%s", compat);

Re: [PATCH RESEND] of: module: add buffer overflow check in of_modalias()

[Rob Herring]

On Sun, Apr 14, 2024 at 11:51:39AM +0300, Sergey Shtylyov wrote:
> In of_modalias(), if the buffer happens to be too small even for the 1st
> snprintf() call, the len parameter will become negative and str parameter
> (if not NULL initially) will point beyond the buffer's end. Add the buffer
> overflow check after the 1st snprintf() call and fix such check after the
> strlen() call (accounting for the terminating NUL char).
> 
> Fixes: bc575064d688 ("of/device: use of_property_for_each_string to parse compatible strings")
> Signed-off-by: Sergey Shtylyov <s.shtylyov@omp.ru>
> 
> ---
> The patch is against the dt/linus branch of Rob Herring's linux.git repo...
> 
>  drivers/of/module.c |    7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)

Applied, thanks.