[PATCH] USB: core: Use `krealloc()` in `usb_cache_string()`

["Bence Csókás via B4 Relay" <devnull+bence98.sch.bme.hu@kernel.org>]

From: Bence Csókás <bence98@sch.bme.hu>

Instead of "shrinking" the allocation by `kmalloc()`ing a new, smaller
buffer, utilize `krealloc()` to shrink the existing allocation. This saves
a `memcpy()`, as well as guards against `smallbuf` allocation failure.

Signed-off-by: Bence Csókás <bence98@sch.bme.hu>
---
Using `krealloc()` makes this code from 2005 more readable as well as
robust. Nested `if`s were also unrolled.
---
 drivers/usb/core/message.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/usb/core/message.c b/drivers/usb/core/message.c
index ea970ddf8879..dfe61d8b913b 100644
--- a/drivers/usb/core/message.c
+++ b/drivers/usb/core/message.c
@@ -1005,7 +1005,7 @@ int usb_string(struct usb_device *dev, int index, char *buf, size_t size)
 }
 EXPORT_SYMBOL_GPL(usb_string);
 
-/* one UTF-8-encoded 16-bit character has at most three bytes */
+/* one 16-bit character, when UTF-8-encoded, has at most three bytes */
 #define MAX_USB_STRING_SIZE (127 * 3 + 1)
 
 /**
@@ -1026,17 +1026,17 @@ char *usb_cache_string(struct usb_device *udev, int index)
 		return NULL;
 
 	buf = kmalloc(MAX_USB_STRING_SIZE, GFP_NOIO);
-	if (buf) {
-		len = usb_string(udev, index, buf, MAX_USB_STRING_SIZE);
-		if (len > 0) {
-			smallbuf = kmalloc(++len, GFP_NOIO);
-			if (!smallbuf)
-				return buf;
-			memcpy(smallbuf, buf, len);
-		}
+	if (!buf)
+		return NULL;
+
+	len = usb_string(udev, index, buf, MAX_USB_STRING_SIZE);
+	if (len <= 0) {
 		kfree(buf);
+		return NULL;
 	}
-	return smallbuf;
+
+	smallbuf = krealloc(buf, len + 1, GFP_NOIO);
+	return smallbuf ? : buf;
 }
 EXPORT_SYMBOL_GPL(usb_cache_string);
 

---
base-commit: 80234b5ab240f52fa45d201e899e207b9265ef91
change-id: 20260311-usb-krealloc-4e413f239a9f

Best regards,
-- 
Bence Csókás <bence98@sch.bme.hu>