From 7d7f794482b74e39d8c0cd830333eb40fc0234d4 Mon Sep 17 00:00:00 2001 From: Lee Jones Date: Thu, 30 Nov 2023 10:54:37 +0000 Subject: [PATCH] usb: fotg210-hcd: Replace snprintf() with the safer scnprintf() variant There is a general misunderstanding amongst engineers that {v}snprintf() returns the length of the data *actually* encoded into the destination array. However, as per the C99 standard {v}snprintf() really returns the length of the data that *would have been* written if there were enough space for it. This misunderstanding has led to buffer-overruns in the past. It's generally considered safer to use the {v}scnprintf() variants in their place (or even sprintf() in simple cases). So let's do that. The uses in this file both seem to assume that data *has been* written! Link: https://lwn.net/Articles/69419/ Link: https://github.com/KSPP/linux/issues/105 Cc: Linus Walleij Cc: Greg Kroah-Hartman Cc: Yuan-Hsin Chen Cc: Feng-Hsin Chiang Cc: Po-Yu Chuang Cc: linux-usb@vger.kernel.org Signed-off-by: Lee Jones Reviewed-by: Linus Walleij Link: https://lore.kernel.org/r/20231130105459.3208986-4-lee@kernel.org Signed-off-by: Greg Kroah-Hartman --- drivers/usb/fotg210/fotg210-hcd.c | 12 ++++-------- 1 file changed, 4 insertions(+), 8 deletions(-) diff --git a/drivers/usb/fotg210/fotg210-hcd.c b/drivers/usb/fotg210/fotg210-hcd.c index 929106c16b29b..b2f8b53cc8ef5 100644 --- a/drivers/usb/fotg210/fotg210-hcd.c +++ b/drivers/usb/fotg210/fotg210-hcd.c @@ -404,9 +404,9 @@ static void qh_lines(struct fotg210_hcd *fotg210, struct fotg210_qh *qh, else if (td->hw_alt_next != list_end) mark = '/'; } - temp = snprintf(next, size, - "\n\t%p%c%s len=%d %08x urb %p", - td, mark, ({ char *tmp; + temp = scnprintf(next, size, + "\n\t%p%c%s len=%d %08x urb %p", + td, mark, ({ char *tmp; switch ((scratch>>8)&0x03) { case 0: tmp = "out"; @@ -424,17 +424,13 @@ static void qh_lines(struct fotg210_hcd *fotg210, struct fotg210_qh *qh, (scratch >> 16) & 0x7fff, scratch, td->urb); - if (size < temp) - temp = size; size -= temp; next += temp; if (temp == size) goto done; } - temp = snprintf(next, size, "\n"); - if (size < temp) - temp = size; + temp = scnprintf(next, size, "\n"); size -= temp; next += temp; -- 2.30.2