[PATCH 5/5] drivers/s390/cio: ensure the copied buf is NULL terminated

[Bui Quang Minh]

Currently, we allocate a lbuf-sized kernel buffer and copy lbuf from
userspace to that buffer. Later, we use scanf on this buffer but we don't
ensure that the string is terminated inside the buffer, this can lead to
OOB read when using scanf. Fix this issue by allocating 1 more byte to at
the end of buffer and write NULL terminator to the end of buffer after
userspace copying.

Fixes: a4f17cc72671 ("s390/cio: add CRW inject functionality")
Signed-off-by: Bui Quang Minh <minhquangbui99@xxxxxxxxx>
---
 drivers/s390/cio/cio_inject.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/cio/cio_inject.c b/drivers/s390/cio/cio_inject.c
index 8613fa937237..9b69fbf49f60 100644
--- a/drivers/s390/cio/cio_inject.c
+++ b/drivers/s390/cio/cio_inject.c
@@ -95,10 +95,11 @@ static ssize_t crw_inject_write(struct file *file, const char __user *buf,
 		return -EINVAL;
 	}
 
-	buffer = vmemdup_user(buf, lbuf);
+	buffer = vmemdup_user(buf, lbuf + 1);
 	if (IS_ERR(buffer))
 		return -ENOMEM;
 
+	buffer[lbuf] = '\0';
 	rc = sscanf(buffer, "%x %x %x %x %x %x %x", &slct, &oflw, &chn, &rsc, &anc,
 		    &erc, &rsid);
 

-- 
2.34.1