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Commit 0fb44559 authored by WANG Cong's avatar WANG Cong Committed by David S. Miller
Browse files

af_unix: move unix_mknod() out of bindlock 



Dmitry reported a deadlock scenario:

unix_bind() path:
u->bindlock ==> sb_writer

do_splice() path:
sb_writer ==> pipe->mutex ==> u->bindlock

In the unix_bind() code path, unix_mknod() does not have to
be done with u->bindlock held, since it is a pure fs operation,
so we can just move unix_mknod() out.

Reported-by: default avatarDmitry Vyukov <dvyukov@google.com>
Tested-by: default avatarDmitry Vyukov <dvyukov@google.com>
Cc: Rainer Weikusat <rweikusat@mobileactivedefense.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: default avatarCong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent a59b7e02

net/unix/af_unix.c

+16 −11
Original line number Diff line number Diff line
@@ -995,6 +995,7 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) 
	unsigned int hash;

	struct unix_address *addr;

	struct hlist_head *list;

	struct path path = { NULL, NULL };



	err = -EINVAL;

	if (sunaddr->sun_family != AF_UNIX)
@@ -1010,9 +1011,20 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) 
		goto out;

	addr_len = err;



	if (sun_path[0]) {

		umode_t mode = S_IFSOCK |

		       (SOCK_INODE(sock)->i_mode & ~current_umask());

		err = unix_mknod(sun_path, mode, &path);

		if (err) {

			if (err == -EEXIST)

				err = -EADDRINUSE;

			goto out;

		}

	}



	err = mutex_lock_interruptible(&u->bindlock);

	if (err)

		goto out;

		goto out_put;



	err = -EINVAL;

	if (u->addr)
@@ -1029,16 +1041,6 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) 
	atomic_set(&addr->refcnt, 1);



	if (sun_path[0]) {

		struct path path;

		umode_t mode = S_IFSOCK |

		       (SOCK_INODE(sock)->i_mode & ~current_umask());

		err = unix_mknod(sun_path, mode, &path);

		if (err) {

			if (err == -EEXIST)

				err = -EADDRINUSE;

			unix_release_addr(addr);

			goto out_up;

		}

		addr->hash = UNIX_HASH_SIZE;

		hash = d_backing_inode(path.dentry)->i_ino & (UNIX_HASH_SIZE - 1);

		spin_lock(&unix_table_lock);
@@ -1065,6 +1067,9 @@ static int unix_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len) 
	spin_unlock(&unix_table_lock);

out_up:

	mutex_unlock(&u->bindlock);

out_put:

	if (err)

		path_put(&path);

out:

	return err;

}