linux-hardening - [PATCH] usb: gadget: function: printer: Replace strlcpy with strscpy

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Date:   Tue, 13 Jun 2023 00:43:41 +0000
From:   Azeem Shaikh <azeemshaikh38@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-hardening@...r.kernel.org,
        Azeem Shaikh <azeemshaikh38@...il.com>,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Albert Briscoe <albertsbriscoe@...il.com>,
        Benjamin Tissoires <benjamin.tissoires@...hat.com>,
        Andrzej Pietrasiewicz <andrzej.p@...labora.com>
Subject: [PATCH] usb: gadget: function: printer: Replace strlcpy with strscpy

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 -E2BIG
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@...il.com>
---
 drivers/usb/gadget/function/f_printer.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/function/f_printer.c b/drivers/usb/gadget/function/f_printer.c
index 28db3e336e7d..10dc7c55c25f 100644
--- a/drivers/usb/gadget/function/f_printer.c
+++ b/drivers/usb/gadget/function/f_printer.c
@@ -1211,8 +1211,8 @@ static ssize_t f_printer_opts_pnp_string_show(struct config_item *item,
 	if (!opts->pnp_string)
 		goto unlock;
 
-	result = strlcpy(page, opts->pnp_string, PAGE_SIZE);
-	if (result >= PAGE_SIZE) {
+	result = strscpy(page, opts->pnp_string, PAGE_SIZE);
+	if (result == -E2BIG) {
 		result = PAGE_SIZE;
 	} else if (page[result - 1] != '\n' && result + 1 < PAGE_SIZE) {
 		page[result++] = '\n';
-- 
2.41.0.162.gfafddb0af9-goog