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authorAli MJ Al-Nasrawy <alimjalnasrawy@gmail.com>2019-09-25 17:47:12 +0300
committerHauke Mehrtens <hauke@hauke-m.de>2019-10-12 23:51:29 +0200
commitc2635b871d1dd03a6608a9255222672decd49e09 (patch)
treee395a23095d78ba2c3a5f667cd10ecc0aaf05698 /package/kernel
parent77cfc0739d30c1282f7de24d2ec086d244e34bb7 (diff)
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trelay: fix deadlock on remove
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 <alimjalnasrawy@gmail.com>
Diffstat (limited to 'package/kernel')
-rw-r--r--package/kernel/trelay/src/trelay.c28
1 files changed, 21 insertions, 7 deletions
diff --git a/package/kernel/trelay/src/trelay.c b/package/kernel/trelay/src/trelay.c
index d09dc07246..3871ace070 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;
@@ -106,16 +110,25 @@ 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;
+ 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();
- ret = trelay_do_remove(tr);
+ list_for_each_entry_safe(tr, tmp, &trelay_devs, list)
+ if (tr->to_remove)
+ trelay_do_remove(tr);
rtnl_unlock();
- if (ret < 0)
- return ret;
-
- return count;
+ return 0;
}
static const struct file_operations fops_remove = {
@@ -123,6 +136,7 @@ static const struct file_operations fops_remove = {
.open = trelay_open,
.write = trelay_remove_write,
.llseek = default_llseek,
+ .release = trelay_remove_release,
};