[PATCH] HID: roccat: fix use-after-free in roccat_report_event

[FirstName LastName <bsevens@google.com>]

From: Benoît Sevens <bsevens@google.com>

roccat_report_event() iterates over the device->readers list without
holding the readers_lock. This allows a concurrent roccat_release() to
remove and free a reader while it's still being accessed, leading to a
use-after-free.

Protect the readers list traversal with the readers_lock mutex.

Signed-off-by: Benoît Sevens <bsevens@google.com>
---
 drivers/hid/hid-roccat.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/hid/hid-roccat.c b/drivers/hid/hid-roccat.c
index fd0ea52f7cba..d6fff53d4ee7 100644
--- a/drivers/hid/hid-roccat.c
+++ b/drivers/hid/hid-roccat.c
@@ -257,6 +257,7 @@ int roccat_report_event(int minor, u8 const *data)
 	if (!new_value)
 		return -ENOMEM;
 
+	mutex_lock(&device->readers_lock);
 	mutex_lock(&device->cbuf_lock);
 
 	report = &device->cbuf[device->cbuf_end];
@@ -279,6 +280,7 @@ int roccat_report_event(int minor, u8 const *data)
 	}
 
 	mutex_unlock(&device->cbuf_lock);
+	mutex_unlock(&device->readers_lock);
 
 	wake_up_interruptible(&device->wait);
 	return 0;
-- 
2.53.0.959.g497ff81fa9-goog