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From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: syzbot <syzbot+7a8ba368b47fdefca61e@syzkaller.appspotmail.com>,
	Alexei Starovoitov <ast@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
	syzkaller-bugs <syzkaller-bugs@googlegroups.com>
Subject: debugfs: fix use-after-free on symlink traversal
Date: Tue, 26 Mar 2019 01:43:37 +0000	[thread overview]
Message-ID: <20190326014337.GX2217@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20190326013858.GU2217@ZenIV.linux.org.uk>

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>
---
diff --git a/fs/debugfs/inode.c b/fs/debugfs/inode.c
index 95b5e78c22b1..f25daa207421 100644
--- a/fs/debugfs/inode.c
+++ b/fs/debugfs/inode.c
@@ -163,19 +163,24 @@ 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 void debugfs_release_dentry(struct dentry *dentry)

  parent reply	other threads:[~2019-03-26  1:43 UTC|newest]

Thread overview: 37+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-28 17:40 KASAN: use-after-free Read in path_lookupat syzbot
2019-03-25  0:44 ` syzbot
2019-03-25  1:25   ` Linus Torvalds
2019-03-25  1:23 ` Linus Torvalds
2019-03-25  4:57   ` Al Viro
2019-03-25  9:15     ` Daniel Borkmann
2019-03-25 11:11       ` Al Viro
2019-03-25 11:17         ` Al Viro
2019-03-25 11:21           ` Daniel Borkmann
2019-03-25 18:36     ` Linus Torvalds
2019-03-25 19:18       ` Linus Torvalds
2019-03-25 21:14         ` Al Viro
2019-03-25 21:45           ` Linus Torvalds
2019-03-25 22:04             ` Daniel Borkmann
2019-03-25 22:13               ` Linus Torvalds
2019-03-25 22:41                 ` Daniel Borkmann
2019-03-25 22:49               ` Al Viro
2019-03-25 23:37             ` Al Viro
2019-03-25 23:44               ` Alexei Starovoitov
2019-03-26  0:21                 ` Al Viro
2019-03-26  1:38               ` ceph: fix use-after-free on symlink traversal Al Viro
2019-03-26  1:39                 ` jffs2: " Al Viro
2019-03-26  1:40                 ` ubifs: " Al Viro
2019-03-26  1:43                 ` Al Viro [this message]
2019-03-26 10:41                 ` ceph: " Jeff Layton
2019-03-26 11:38                 ` Ilya Dryomov
2019-03-26  1:45               ` KASAN: use-after-free Read in path_lookupat Al Viro
2019-04-10 18:11                 ` Al Viro
2019-04-10 19:44                   ` Linus Torvalds
2019-03-25 19:43       ` Al Viro
2019-03-25 22:48         ` Dave Chinner
2019-03-25 23:02           ` Al Viro
     [not found]             ` <CAGe7X7mb=gK7zhSwmT_6mmmkcbjhZAOb=wj31BdUcHkNUPsm2Q@mail.gmail.com>
2019-03-26  4:15               ` Al Viro
2019-03-27 16:58                 ` Jan Kara
2019-03-27 18:59                   ` Al Viro
2019-03-28  9:00                     ` Jan Kara
2019-03-27 17:22             ` Jan Kara

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