[PATCH 5.10 084/108] usb: gadget: configfs: Prevent OOB read/write in usb_string_copy()

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5.10-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lee Jones <lee@xxxxxxxxxx>

commit 6d3c721e686ea6c59e18289b400cc95c76e927e0 upstream.

Userspace provided string 's' could trivially have the length zero. Left
unchecked this will firstly result in an OOB read in the form
`if (str[0 - 1] == '\n') followed closely by an OOB write in the form
`str[0 - 1] = '\0'`.

There is already a validating check to catch strings that are too long.
Let's supply an additional check for invalid strings that are too short.

Signed-off-by: Lee Jones <lee@xxxxxxxxxx>
Cc: stable <stable@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20240705074339.633717-1-lee@xxxxxxxxxx
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/usb/gadget/configfs.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/drivers/usb/gadget/configfs.c
+++ b/drivers/usb/gadget/configfs.c
@@ -104,9 +104,12 @@ static int usb_string_copy(const char *s
 	int ret;
 	char *str;
 	char *copy = *s_copy;
+
 	ret = strlen(s);
 	if (ret > USB_MAX_STRING_LEN)
 		return -EOVERFLOW;
+	if (ret < 1)
+		return -EINVAL;
 
 	if (copy) {
 		str = copy;






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