Patch "of: module: add buffer overflow check in of_modalias()" has been added to the 6.9-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    of: module: add buffer overflow check in of_modalias()

to the 6.9-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     of-module-add-buffer-overflow-check-in-of_modalias.patch
and it can be found in the queue-6.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit c51e5acd7bf5303cfe59ea375301e527f70bd04d
Author: Sergey Shtylyov <s.shtylyov@xxxxxx>
Date:   Sun Apr 14 11:51:39 2024 +0300

    of: module: add buffer overflow check in of_modalias()
    
    [ Upstream commit cf7385cb26ac4f0ee6c7385960525ad534323252 ]
    
    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@xxxxxx>
    Link: https://lore.kernel.org/r/bbfc6be0-c687-62b6-d015-5141b93f313e@xxxxxx
    Signed-off-by: Rob Herring <robh@xxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/of/module.c b/drivers/of/module.c
index f58e624953a20..780fd82a7ecc5 100644
--- a/drivers/of/module.c
+++ b/drivers/of/module.c
@@ -29,14 +29,15 @@ ssize_t of_modalias(const struct device_node *np, char *str, ssize_t len)
 	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);