Upon writing to "remove" file, debugfs_remove_recursive() blocks while
holding rtnl_lock. This is because debugfs' file_ops callbacks are
executed in debugfs_use_file_*() context which prevents file removal.
Fix this by only flagging the device for removal and then do the cleanup
in file_ops.release callback which is executed out of that context.
Signed-off-by: Ali MJ Al-Nasrawy <alimjalnasr...@gmail.com>
---
package/kernel/trelay/src/trelay.c | 32 +++++++++++++++++++++---------
1 file changed, 23 insertions(+), 9 deletions(-)
diff --git a/package/kernel/trelay/src/trelay.c
b/package/kernel/trelay/src/trelay.c
index 6d9d9cc14b..0e3d85bfef 100644
--- a/package/kernel/trelay/src/trelay.c
+++ b/package/kernel/trelay/src/trelay.c
@@ -27,6 +27,7 @@ struct trelay {
struct list_head list;
struct net_device *dev1, *dev2;
struct dentry *debugfs;
+ int to_remove;
char name[];
};
@@ -60,13 +61,16 @@ static int trelay_do_remove(struct trelay *tr)
{
list_del(&tr->list);
+ /* First and before all, ensure that the debugfs file is removed
+ * to prevent dangling pointer in file->private_data */
+ debugfs_remove_recursive(tr->debugfs);
+
dev_put(tr->dev1);
dev_put(tr->dev2);
netdev_rx_handler_unregister(tr->dev1);
netdev_rx_handler_unregister(tr->dev2);
- debugfs_remove_recursive(tr->debugfs);
kfree(tr);
return 0;
@@ -106,23 +110,33 @@ static ssize_t trelay_remove_write(struct file *file,
const char __user *ubuf,
size_t count, loff_t *ppos)
{
struct trelay *tr = file->private_data;
- int ret;
-
- rtnl_lock();
- ret = trelay_do_remove(tr);
- rtnl_unlock();
-
- if (ret < 0)
- return ret;
+ tr->to_remove = 1;
return count;
}
+static int trelay_remove_release(struct inode *inode, struct file *file)
+{
+ struct trelay *tr, *tmp;
+
+ /* This is the only file op that is called outside debugfs_use_file_*()
+ * context which means that: (1) this file can be removed and
+ * (2) file->private_data may no longer be valid */
+ rtnl_lock();
+ list_for_each_entry_safe(tr, tmp, &trelay_devs, list)
+ if (tr->to_remove)
+ trelay_do_remove(tr);
+ rtnl_unlock();
+
+ return 0;
+}
+
static const struct file_operations fops_remove = {
.owner = THIS_MODULE,
.open = trelay_open,
.write = trelay_remove_write,
.llseek = default_llseek,
+ .release = trelay_remove_release,
};
--
2.23.0
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