Re: [PATCH v4 01/11] stm class: Introduce an abstraction for System Trace Module devices

On 09/22/2015 08:47 AM, Alexander Shishkin wrote:

+static ssize_t stm_char_write(struct file *file, const char __user *buf,
+			      size_t count, loff_t *ppos)
+{
+	struct stm_file *stmf = file->private_data;
+	struct stm_device *stm = stmf->stm;
+	char *kbuf;
+	int err;
+
+	/*
+	 * if no m/c have been assigned to this writer up to this
+	 * point, use "default" policy entry
+	 */
+	if (!stmf->output.nr_chans) {
+		err = stm_file_assign(stmf, "default", 1);
+		/*
+		 * EBUSY means that somebody else just assigned this
+		 * output, which is just fine for write()
+		 */
+		if (err && err != -EBUSY)
+			return err;
+	}
+
+	kbuf = kmalloc(count + 1, GFP_KERNEL);

This bit allows for user-controllable kmalloc() allocation lengths, including
a possible overflow.


Thanks,
Sasha