[PATCH] Platform: OLPC: uninitialized data in debugfs write

From: Dan Carpenter <dan.carpenter@oracle.com>
To: Hans de Goede <hdegoede@redhat.com>,
	Andres Salomon <dilinger@queued.net>
Cc: Mark Gross <markgross@kernel.org>,
	platform-driver-x86@vger.kernel.org,
	kernel-janitors@vger.kernel.org
Subject: [PATCH] Platform: OLPC: uninitialized data in debugfs write
Date: Wed, 20 Jul 2022 21:23:38 +0300	[thread overview]
Message-ID: <YthIKn+TfZSZMEcM@kili> (raw)

The call to:

	size = simple_write_to_buffer(cmdbuf, sizeof(cmdbuf), ppos, buf, size);

will succeed if at least one byte is written to the "cmdbuf" buffer.
The "*ppos" value controls which byte is written.  Another problem is
that this code does not check for errors so it's possible for the entire
buffer to be unintialized.

Inintialize the struct to zero to prevent reading uninitialized stack
data.

Debugfs is normally only writable by root so the impact of this bug is
very minimal.

Fixes: 6cca83d498bd ("Platform: OLPC: move debugfs support from x86 EC driver")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
---
The ec_dbgfs_cmd_write() function is not great.  We could copy the data
outside the lock for example.  But that's outside the scope of this
patch.

 drivers/platform/olpc/olpc-ec.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/platform/olpc/olpc-ec.c b/drivers/platform/olpc/olpc-ec.c
index 4ff5c3a12991..921520475ff6 100644
--- a/drivers/platform/olpc/olpc-ec.c
+++ b/drivers/platform/olpc/olpc-ec.c
@@ -264,7 +264,7 @@ static ssize_t ec_dbgfs_cmd_write(struct file *file, const char __user *buf,
 	int i, m;
 	unsigned char ec_cmd[EC_MAX_CMD_ARGS];
 	unsigned int ec_cmd_int[EC_MAX_CMD_ARGS];
-	char cmdbuf[64];
+	char cmdbuf[64] = "";
 	int ec_cmd_bytes;
 
 	mutex_lock(&ec_dbgfs_lock);
-- 
2.35.1

