input: libps2: mark data received in __ps2_command() as initialized

KMSAN does not know that the device initializes certain bytes in
ps2dev->cmdbuf.  Call kmsan_unpoison_memory() to explicitly mark them as
initialized.

Link: https://lkml.kernel.org/r/20220915150417.722975-21-glider@google.comSigned-off-by: Alexander Potapenko <glider@google.com>
Cc: Alexander Viro <viro@zeniv.linux.org.uk>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrey Konovalov <andreyknvl@gmail.com>
Cc: Andrey Konovalov <andreyknvl@google.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers@google.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Ilya Leoshkevich <iii@linux.ibm.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Kees Cook <keescook@chromium.org>
Cc: Marco Elver <elver@google.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Petr Mladek <pmladek@suse.com>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Vegard Nossum <vegard.nossum@oracle.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

drivers/input/serio/libps2.c

@@ -12,6 +12,7 @@
 #include <linux/sched.h>
 #include <linux/interrupt.h>
 #include <linux/input.h>
+#include <linux/kmsan-checks.h>
 #include <linux/serio.h>
 #include <linux/i8042.h>
 #include <linux/libps2.h>
@@ -294,9 +295,11 @@ int __ps2_command(struct ps2dev *ps2dev, u8 *param, unsigned int command)
 
 	serio_pause_rx(ps2dev->serio);
 
-	if (param)
+	if (param) {
 		for (i = 0; i < receive; i++)
 			param[i] = ps2dev->cmdbuf[(receive - 1) - i];
+		kmsan_unpoison_memory(param, receive);
+	}
 
 	if (ps2dev->cmdcnt &&
 	    (command != PS2_CMD_RESET_BAT || ps2dev->cmdcnt != 1)) {