Commit 93b919da authored by Al Viro's avatar Al Viro

debugfs: fix use-after-free on symlink traversal

symlink body shouldn't be freed without an RCU delay.  Switch debugfs to
->destroy_inode() and use of call_rcu(); free both the inode and symlink
body in the callback.  Similar to solution for bpf, only here it's even
more obvious that ->evict_inode() can be dropped.
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 0cdc17eb
...@@ -163,19 +163,24 @@ static int debugfs_show_options(struct seq_file *m, struct dentry *root) ...@@ -163,19 +163,24 @@ static int debugfs_show_options(struct seq_file *m, struct dentry *root)
return 0; return 0;
} }
static void debugfs_evict_inode(struct inode *inode) static void debugfs_i_callback(struct rcu_head *head)
{ {
truncate_inode_pages_final(&inode->i_data); struct inode *inode = container_of(head, struct inode, i_rcu);
clear_inode(inode);
if (S_ISLNK(inode->i_mode)) if (S_ISLNK(inode->i_mode))
kfree(inode->i_link); kfree(inode->i_link);
free_inode_nonrcu(inode);
}
static void debugfs_destroy_inode(struct inode *inode)
{
call_rcu(&inode->i_rcu, debugfs_i_callback);
} }
static const struct super_operations debugfs_super_operations = { static const struct super_operations debugfs_super_operations = {
.statfs = simple_statfs, .statfs = simple_statfs,
.remount_fs = debugfs_remount, .remount_fs = debugfs_remount,
.show_options = debugfs_show_options, .show_options = debugfs_show_options,
.evict_inode = debugfs_evict_inode, .destroy_inode = debugfs_destroy_inode,
}; };
static void debugfs_release_dentry(struct dentry *dentry) static void debugfs_release_dentry(struct dentry *dentry)
......
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