[PATCH AUTOSEL 4.9 15/28] debugfs: fix use-after-free on symlink traversal
From: Sasha Levin <sashal@kernel.org>
Date: 2019-04-24 14:55:41
Also in:
bpf, lkml, netdev
Subsystem:
driver core, kobjects, debugfs and sysfs, filesystems (vfs and infrastructure), the rest · Maintainers:
Greg Kroah-Hartman, "Rafael J. Wysocki", Danilo Krummrich, Alexander Viro, Christian Brauner, Linus Torvalds
From: Al Viro <viro@zeniv.linux.org.uk> [ Upstream commit 93b919da64c15b90953f96a536e5e61df896ca57 ] 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: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Sasha Levin <sashal@kernel.org> --- fs/debugfs/inode.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 77e9cd7a0137..20ee612017bf 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c@@ -170,19 +170,24 @@ static int debugfs_show_options(struct seq_file *m, struct dentry *root) 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); - clear_inode(inode); + struct inode *inode = container_of(head, struct inode, i_rcu); if (S_ISLNK(inode->i_mode)) 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 = { .statfs = simple_statfs, .remount_fs = debugfs_remount, .show_options = debugfs_show_options, - .evict_inode = debugfs_evict_inode, + .destroy_inode = debugfs_destroy_inode, }; static struct vfsmount *debugfs_automount(struct path *path)
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2.19.1