socket: CVE-2018-12232

socket: close race condition between sock_close() and sockfs_setattr()

Reference:
https://nvd.nist.gov/vuln/detail/CVE-2018-12232
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=91717ffc9057f38a0203a40ef36ae2e482fd7cbe

Change-Id: If7db46c2af9d629c5311f5d901943289084566a9
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>

1 files changed, 98 insertions, 0 deletions

diff --git a/patches/cve/CVE-2018-12232-socket-close-race-condition-between-sock_close-and-s.patch b/patches/cve/CVE-2018-12232-socket-close-race-condition-between-sock_close-and-s.patch
new file mode 100644
index 0000000..2dabfe5
--- /dev/null
+++ b/patches/cve/CVE-2018-12232-socket-close-race-condition-between-sock_close-and-s.patch
@@ -0,0 +1,98 @@
+From 91717ffc9057f38a0203a40ef36ae2e482fd7cbe Mon Sep 17 00:00:00 2001
+From: Cong Wang <xiyou.wangcong@gmail.com>
+Date: Thu, 7 Jun 2018 13:39:49 -0700
+Subject: [PATCH] socket: close race condition between sock_close() and
+ sockfs_setattr()
+
+[ Upstream commit 6d8c50dcb029872b298eea68cc6209c866fd3e14 ]
+
+fchownat() doesn't even hold refcnt of fd until it figures out
+fd is really needed (otherwise is ignored) and releases it after
+it resolves the path. This means sock_close() could race with
+sockfs_setattr(), which leads to a NULL pointer dereference
+since typically we set sock->sk to NULL in ->release().
+
+As pointed out by Al, this is unique to sockfs. So we can fix this
+in socket layer by acquiring inode_lock in sock_close() and
+checking against NULL in sockfs_setattr().
+
+sock_release() is called in many places, only the sock_close()
+path matters here. And fortunately, this should not affect normal
+sock_close() as it is only called when the last fd refcnt is gone.
+It only affects sock_close() with a parallel sockfs_setattr() in
+progress, which is not common.
+
+CVE: CVE-2018-12232
+Upstream-Status: Backport [https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.14.y&id=91717ffc9057f38a0203a40ef36ae2e482fd7cbe]
+
+Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.")
+Reported-by: shankarapailoor <shankarapailoor@gmail.com>
+Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
+Cc: Lorenzo Colitti <lorenzo@google.com>
+Cc: Al Viro <viro@zeniv.linux.org.uk>
+Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
+---
+ net/socket.c | 18 +++++++++++++++---
+ 1 file changed, 15 insertions(+), 3 deletions(-)
+
+diff --git a/net/socket.c b/net/socket.c
+index 43d2f17f5eea..8b2bef6cfe42 100644
+--- a/net/socket.c
++++ b/net/socket.c
+@@ -538,7 +538,10 @@ static int sockfs_setattr(struct dentry *dentry, struct iattr *iattr)
+        if (!err && (iattr->ia_valid & ATTR_UID)) {
+                struct socket *sock = SOCKET_I(d_inode(dentry));
+ 
+-               sock->sk->sk_uid = iattr->ia_uid;
++               if (sock->sk)
++                       sock->sk->sk_uid = iattr->ia_uid;
++               else
++                       err = -ENOENT;
+        }
+ 
+        return err;
+@@ -588,12 +591,16 @@ EXPORT_SYMBOL(sock_alloc);
+  *     an inode not a file.
+  */
+ 
+-void sock_release(struct socket *sock)
++static void __sock_release(struct socket *sock, struct inode *inode)
+ {
+        if (sock->ops) {
+                struct module *owner = sock->ops->owner;
+ 
++               if (inode)
++                       inode_lock(inode);
+                sock->ops->release(sock);
++               if (inode)
++                       inode_unlock(inode);
+                sock->ops = NULL;
+                module_put(owner);
+        }
+@@ -608,6 +615,11 @@ void sock_release(struct socket *sock)
+        }
+        sock->file = NULL;
+ }
++
++void sock_release(struct socket *sock)
++{
++       __sock_release(sock, NULL);
++}
+ EXPORT_SYMBOL(sock_release);
+ 
+ void __sock_tx_timestamp(__u16 tsflags, __u8 *tx_flags)
+@@ -1122,7 +1134,7 @@ static int sock_mmap(struct file *file, struct vm_area_struct *vma)
+ 
+ static int sock_close(struct inode *inode, struct file *filp)
+ {
+-       sock_release(SOCKET_I(inode));
++       __sock_release(SOCKET_I(inode), inode);
+        return 0;
+ }
+ 
+-- 
+2.20.1
+