hdev->debug_list->hid_debug_buf is not protected from concurrent updates
from the writer, hid_debug_event() and reads by the reader,
hid_debug_events_read(). Fix this by adding per-list-element spinlock.
Also introduce a temporary buffer tempbuf so copy_to_user() is not called
from under a spinlock.
Signed-off-by: Vladis Dronov <vdro...@redhat.com>
---
drivers/hid/hid-debug.c | 47 +++++++++++++++++++++++----------------
include/linux/hid-debug.h | 1 +
2 files changed, 29 insertions(+), 19 deletions(-)
diff --git a/drivers/hid/hid-debug.c b/drivers/hid/hid-debug.c
index 20580871b0ec..e827784baf1a 100644
--- a/drivers/hid/hid-debug.c
+++ b/drivers/hid/hid-debug.c
@@ -663,15 +663,17 @@ void hid_debug_event(struct hid_device *hdev, char *buf)
{
unsigned i;
struct hid_debug_list *list;
- unsigned long flags;
+ unsigned long flags, flags2;
spin_lock_irqsave(&hdev->debug_list_lock, flags);
list_for_each_entry(list, &hdev->debug_list, node) {
+ spin_lock_irqsave(&list->list_lock, flags2);
for (i = 0; buf[i]; i++)
list->hid_debug_buf[(list->tail + i) %
HID_DEBUG_BUFSIZE] =
buf[i];
list->tail = (list->tail + i) % HID_DEBUG_BUFSIZE;
- }
+ spin_unlock_irqrestore(&list->list_lock, flags2);
+ }
spin_unlock_irqrestore(&hdev->debug_list_lock, flags);
wake_up_interruptible(&hdev->debug_wait);
@@ -1095,6 +1097,7 @@ static int hid_debug_events_open(struct inode *inode,
struct file *file)
}
list->hdev = (struct hid_device *) inode->i_private;
file->private_data = list;
+ spin_lock_init(&list->list_lock);
mutex_init(&list->read_mutex);
spin_lock_irqsave(&list->hdev->debug_list_lock, flags);
@@ -1109,6 +1112,8 @@ static ssize_t hid_debug_events_read(struct file *file,
char __user *buffer,
size_t count, loff_t *ppos)
{
struct hid_debug_list *list = file->private_data;
+ char *tmpbuf;
+ unsigned long flags;
int ret = 0, len;
DECLARE_WAITQUEUE(wait, current);
@@ -1151,10 +1156,18 @@ static ssize_t hid_debug_events_read(struct file *file,
char __user *buffer,
if (ret)
goto out;
- /* pass the ringbuffer content to userspace */
+ tmpbuf = kmalloc(min_t(size_t, count, HID_DEBUG_BUFSIZE),
+ GFP_KERNEL|__GFP_NOWARN);
+ if (!tmpbuf) {
+ ret = -ENOMEM;
+ goto out;
+ }
+
+ /* lock and copy the ringbuffer content to tmpbuf */
+ spin_lock_irqsave(&list->list_lock, flags);
copy_rest:
if (list->tail == list->head)
- goto out;
+ goto out_unlock;
/* the data from the head to the tail in the buffer is linear */
if (list->tail > list->head) {
@@ -1162,11 +1174,7 @@ static ssize_t hid_debug_events_read(struct file *file,
char __user *buffer,
if (len > count)
len = count;
- if (copy_to_user(buffer + ret,
- &list->hid_debug_buf[list->head], len)) {
- ret = -EFAULT;
- goto out;
- }
+ memcpy(tmpbuf + ret, &list->hid_debug_buf[list->head], len);
ret += len;
list->head += len;
} else {
@@ -1180,19 +1188,11 @@ static ssize_t hid_debug_events_read(struct file *file,
char __user *buffer,
if (len > count) {
len = count;
- if (copy_to_user(buffer,
- &list->hid_debug_buf[list->head], len)) {
- ret = -EFAULT;
- goto out;
- }
+ memcpy(tmpbuf, &list->hid_debug_buf[list->head], len);
ret += len;
list->head += len;
} else {
- if (copy_to_user(buffer,
- &list->hid_debug_buf[list->head], len)) {
- ret = -EFAULT;
- goto out;
- }
+ memcpy(tmpbuf, &list->hid_debug_buf[list->head], len);
list->head = 0;
ret += len;
count -= len;
@@ -1202,6 +1202,15 @@ static ssize_t hid_debug_events_read(struct file *file,
char __user *buffer,
goto copy_rest;
}
}
+
+out_unlock:
+ spin_unlock_irqrestore(&list->list_lock, flags);
+
+ /* copy out tmpbuf content to userspace */
+ if (ret && copy_to_user(buffer, tmpbuf, ret))
+ ret = -EFAULT;
+ kfree(tmpbuf);
+
out:
mutex_unlock(&list->read_mutex);
return ret;
diff --git a/include/linux/hid-debug.h b/include/linux/hid-debug.h
index 8663f216c563..f58665651cb5 100644
--- a/include/linux/hid-debug.h
+++ b/include/linux/hid-debug.h
@@ -45,6 +45,7 @@ struct hid_debug_list {
struct fasync_struct *fasync;
struct hid_device *hdev;
struct list_head node;
+ spinlock_t list_lock;
struct mutex read_mutex;
};
--
2.19.0
