[PATCH 00/12] usb: Replace {v}snprintf() variants with safer alternatives

This series is part of an effort to rid {v}snprintf() where possible.

For a far better description of the problem than I could author, see
Jon's write-up on LWN [1] and/or Alex's on the Kernel Self Protection
Project [1].

[0] https://lwn.net/Articles/69419/
[1] https://github.com/KSPP/linux/issues/105

Lee Jones (12):
  usb: gadget: configfs: Replace snprintf() with the safer scnprintf()
    variant
  usb: gadget: f_uac1: Replace snprintf() with the safer scnprintf()
    variant
  usb: gadget: f_uac2: Replace snprintf() with the safer scnprintf()
    variant
  usb: gadget: uvc: Replace snprintf() with the safer scnprintf()
    variant
  usb: gadget: udc: atmel: Replace snprintf() with the safer scnprintf()
    variant
  usb: cdns2: Replace snprintf() with the safer scnprintf() variant
  usb: host: max3421-hcd: Replace snprintf() with the safer scnprintf()
    variant
  usb: yurex: Replace snprintf() with the safer scnprintf() variant
  usb: mon_stat: Replace snprintf() with the safer scnprintf() variant
  usb: mon_text: Replace snprintf() with the safer scnprintf() variant
  usb: phy: twl6030: Remove snprintf() from sysfs call-backs and replace
    with sysfs_emit()
  usb: storage: Remove snprintf() from sysfs call-backs and replace with
    sysfs_emit()

 drivers/usb/gadget/configfs.c              |  11 +-
 drivers/usb/gadget/function/f_uac1.c       |   6 +-
 drivers/usb/gadget/function/f_uac2.c       |   6 +-
 drivers/usb/gadget/function/uvc_configfs.c |   2 +-
 drivers/usb/gadget/udc/atmel_usba_udc.c    |   3 +-
 drivers/usb/gadget/udc/cdns2/cdns2-debug.h | 138 ++++++++++-----------
 drivers/usb/host/max3421-hcd.c             |  18 +--
 drivers/usb/misc/yurex.c                   |  12 +-
 drivers/usb/mon/mon_stat.c                 |   6 +-
 drivers/usb/mon/mon_text.c                 |  28 +----
 drivers/usb/phy/phy-twl6030-usb.c          |   8 +-
 drivers/usb/storage/sierra_ms.c            |  16 +--
 12 files changed, 120 insertions(+), 134 deletions(-)

Cc: Alan Stern <stern@rowland.harvard.edu>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Andrzej Pietrasiewicz <andrzejtp2010@gmail.com>
Cc: Bryan Wu <cooloney@kernel.org>
Cc: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Cc: Cristian Birsan <cristian.birsan@microchip.com>
Cc: Daniel Scally <dan.scally@ideasonboard.com>
Cc: Hema HK <redacted>
Cc: James Gruber <redacted>
Cc: Jaswinder Singh <redacted>
Cc: Julian Scheel <redacted>
Cc: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Pawel Laszczak <pawell@cadence.com>
Cc: Ruslan Bilovol <redacted>
Cc: Tomoki Sekiyama <redacted>
Cc: usb-storage@lists.one-eyed-alien.net
Cc: Yadwinder Singh <redacted>
-- 
2.43.0.472.g3155946c3a-goog


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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.

Link: https://lwn.net/Articles/69419/
Link: https://github.com/KSPP/linux/issues/105
Cc: Cristian Birsan <cristian.birsan@microchip.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Lee Jones <lee@kernel.org>
---
 drivers/usb/gadget/udc/atmel_usba_udc.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/usb/gadget/udc/atmel_usba_udc.c b/drivers/usb/gadget/udc/atmel_usba_udc.c
index 02b1bef5e22e2..b76885d78e8a7 100644
--- a/drivers/usb/gadget/udc/atmel_usba_udc.c
+++ b/drivers/usb/gadget/udc/atmel_usba_udc.c

@@ -94,7 +94,7 @@ static ssize_t queue_dbg_read(struct file *file, char __user *buf,
 
 	inode_lock(file_inode(file));
 	list_for_each_entry_safe(req, tmp_req, queue, queue) {
-		len = snprintf(tmpbuf, sizeof(tmpbuf),
+		len = scnprintf(tmpbuf, sizeof(tmpbuf),
 				"%8p %08x %c%c%c %5d %c%c%c\n",
 				req->req.buf, req->req.length,
 				req->req.no_interrupt ? 'i' : 'I',

@@ -104,7 +104,6 @@ static ssize_t queue_dbg_read(struct file *file, char __user *buf,
 				req->submitted ? 'F' : 'f',
 				req->using_dma ? 'D' : 'd',
 				req->last_transaction ? 'L' : 'l');
-		len = min(len, sizeof(tmpbuf));
 		if (len > nbytes)
 			break;
 

-- 
2.43.0.472.g3155946c3a-goog


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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.

Link: https://lwn.net/Articles/69419/
Link: https://github.com/KSPP/linux/issues/105
Cc: Cristian Birsan <cristian.birsan@microchip.com>
Cc: Nicolas Ferre <nicolas.ferre@microchip.com>
Cc: Alexandre Belloni <alexandre.belloni@bootlin.com>
Cc: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Cc: linux-arm-kernel@lists.infradead.org
Signed-off-by: Lee Jones <lee@kernel.org>
---
 drivers/usb/host/max3421-hcd.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/usb/host/max3421-hcd.c b/drivers/usb/host/max3421-hcd.c
index d152d72de1269..9fe4f48b18980 100644
--- a/drivers/usb/host/max3421-hcd.c
+++ b/drivers/usb/host/max3421-hcd.c

@@ -1158,12 +1158,12 @@ dump_eps(struct usb_hcd *hcd)
 		end = dp + sizeof(ubuf);
 		*dp = '\0';
 		list_for_each_entry(urb, &ep->urb_list, urb_list) {
-			ret = snprintf(dp, end - dp, " %p(%d.%s %d/%d)", urb,
-				       usb_pipetype(urb->pipe),
-				       usb_urb_dir_in(urb) ? "IN" : "OUT",
-				       urb->actual_length,
-				       urb->transfer_buffer_length);
-			if (ret < 0 || ret >= end - dp)
+			ret = scnprintf(dp, end - dp, " %p(%d.%s %d/%d)", urb,
+					usb_pipetype(urb->pipe),
+					usb_urb_dir_in(urb) ? "IN" : "OUT",
+					urb->actual_length,
+					urb->transfer_buffer_length);
+			if (ret == end - dp - 1)
 				break;	/* error or buffer full */
 			dp += ret;
 		}

@@ -1255,9 +1255,9 @@ max3421_handle_irqs(struct usb_hcd *hcd)
 			end = sbuf + sizeof(sbuf);
 			*dp = '\0';
 			for (i = 0; i < 16; ++i) {
-				int ret = snprintf(dp, end - dp, " %lu",
-						   max3421_hcd->err_stat[i]);
-				if (ret < 0 || ret >= end - dp)
+				int ret = scnprintf(dp, end - dp, " %lu",
+						    max3421_hcd->err_stat[i]);
+				if (ret == end - dp - 1)
 					break;	/* error or buffer full */
 				dp += ret;
 			}

-- 
2.43.0.472.g3155946c3a-goog


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