88 lines
2.7 KiB
Diff
88 lines
2.7 KiB
Diff
From: Cong Wang <xiyou.wangcong@gmail.com>
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Date: Thu, 7 Jun 2018 13:39:49 -0700
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Subject: socket: close race condition between sock_close() and
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sockfs_setattr()
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Origin: https://git.kernel.org/linus/6d8c50dcb029872b298eea68cc6209c866fd3e14
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Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2018-12232
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fchownat() doesn't even hold refcnt of fd until it figures out
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fd is really needed (otherwise is ignored) and releases it after
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it resolves the path. This means sock_close() could race with
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sockfs_setattr(), which leads to a NULL pointer dereference
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since typically we set sock->sk to NULL in ->release().
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As pointed out by Al, this is unique to sockfs. So we can fix this
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in socket layer by acquiring inode_lock in sock_close() and
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checking against NULL in sockfs_setattr().
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sock_release() is called in many places, only the sock_close()
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path matters here. And fortunately, this should not affect normal
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sock_close() as it is only called when the last fd refcnt is gone.
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It only affects sock_close() with a parallel sockfs_setattr() in
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progress, which is not common.
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Fixes: 86741ec25462 ("net: core: Add a UID field to struct sock.")
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Reported-by: shankarapailoor <shankarapailoor@gmail.com>
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Cc: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
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Cc: Lorenzo Colitti <lorenzo@google.com>
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Cc: Al Viro <viro@zeniv.linux.org.uk>
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Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
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Signed-off-by: David S. Miller <davem@davemloft.net>
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---
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net/socket.c | 18 +++++++++++++++---
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1 file changed, 15 insertions(+), 3 deletions(-)
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--- a/net/socket.c
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+++ b/net/socket.c
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@@ -537,7 +537,10 @@ static int sockfs_setattr(struct dentry
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if (!err && (iattr->ia_valid & ATTR_UID)) {
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struct socket *sock = SOCKET_I(d_inode(dentry));
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- sock->sk->sk_uid = iattr->ia_uid;
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+ if (sock->sk)
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+ sock->sk->sk_uid = iattr->ia_uid;
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+ else
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+ err = -ENOENT;
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}
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return err;
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@@ -586,12 +589,16 @@ EXPORT_SYMBOL(sock_alloc);
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* an inode not a file.
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*/
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-void sock_release(struct socket *sock)
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+static void __sock_release(struct socket *sock, struct inode *inode)
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{
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if (sock->ops) {
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struct module *owner = sock->ops->owner;
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+ if (inode)
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+ inode_lock(inode);
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sock->ops->release(sock);
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+ if (inode)
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+ inode_unlock(inode);
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sock->ops = NULL;
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module_put(owner);
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}
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@@ -605,6 +612,11 @@ void sock_release(struct socket *sock)
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}
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sock->file = NULL;
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}
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+
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+void sock_release(struct socket *sock)
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+{
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+ __sock_release(sock, NULL);
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+}
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EXPORT_SYMBOL(sock_release);
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void __sock_tx_timestamp(__u16 tsflags, __u8 *tx_flags)
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@@ -1146,7 +1158,7 @@ static int sock_mmap(struct file *file,
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static int sock_close(struct inode *inode, struct file *filp)
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{
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- sock_release(SOCKET_I(inode));
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+ __sock_release(SOCKET_I(inode), inode);
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return 0;
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}
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