[PATCH] usb: usbtmc: initialize memory written to device

[Pimyn Girgis bemenboshra2001@gmail.com]

Avoid kernel-usb-infoleak by initializing all memory written to device.
The buffer length uses 32bit alignment which might cause some buffer
data to be read without any initialization.

Reported-by: syzbot+8f282cce71948071c335@syzkaller.appspotmail.com
Closes: https://lore.kernel.org/all/0000000000006f6622061eb52dba@google.com/T/
Signed-off-by: Pimyn Girgis <bemenboshra2001@gmail.com> (Google)
---
 drivers/usb/class/usbtmc.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/class/usbtmc.c b/drivers/usb/class/usbtmc.c
index ffc9c6fdd7e1..d79a08dfb54d 100644
--- a/drivers/usb/class/usbtmc.c
+++ b/drivers/usb/class/usbtmc.c
@@ -21,6 +21,7 @@
 #include <linux/usb.h>
 #include <linux/compat.h>
 #include <linux/usb/tmc.h>
+#include <linux/string.h>
 
 /* Increment API VERSION when changing tmc.h with new flags or ioctls
  * or when changing a significant behavior of the driver.
@@ -1169,6 +1170,8 @@ static ssize_t usbtmc_generic_write(struct usbtmc_file_data *file_data,
 		 * (size + 3 & ~3) rounds up and simplifies user code
 		 */
 		aligned = (this_part + 3) & ~3;
+		/* Initialize the remaining part of the buffer */
+		memzero_explicit(buffer + this_part, aligned - this_part);
 		dev_dbg(dev, "write(size:%u align:%u done:%u)\n",
 			(unsigned int)this_part,
 			(unsigned int)aligned,
-- 
2.47.0.rc0.187.ge670bccf7e-goog