[PATCH 6/8] unix_bind_bsd(): move done_path_create() call after dealing with ->bindlock
From: Al Viro <viro@zeniv.linux.org.uk>
Date: 2021-02-22 19:16:38
Also in:
linux-fsdevel, netdev
Subsystem:
networking [general], networking [unix sockets], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Linus Torvalds
Final preparations for doing unlink on failure past the successful mknod. We can't hold ->bindlock over ->mknod() or ->unlink(), since either might do sb_start_write() (e.g. on overlayfs). However, we can do it while holding filesystem and VFS locks - doing kern_path_create() vfs_mknod() grab ->bindlock if u->addr had been set drop ->bindlock done_path_create return -EINVAL else assign the address to socket drop ->bindlock done_path_create return 0 would be deadlock-free. Here we massage unix_bind_bsd() to that form. We are still doing equivalent transformations. Next commit will *not* be an equivalent transformation - it will add a call of vfs_unlink() before done_path_create() in "alread bound" case. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk> --- net/unix/af_unix.c | 26 +++++++++++--------------- 1 file changed, 11 insertions(+), 15 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 5e04e16e6b88..368376621111 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c@@ -988,7 +988,7 @@ static int unix_bind_bsd(struct sock *sk, struct unix_address *addr) struct unix_sock *u = unix_sk(sk); umode_t mode = S_IFSOCK | (SOCK_INODE(sk->sk_socket)->i_mode & ~current_umask()); - struct path parent, path; + struct path parent; struct dentry *dentry; unsigned int hash; int err;
@@ -1005,36 +1005,32 @@ static int unix_bind_bsd(struct sock *sk, struct unix_address *addr) * All right, let's create it. */ err = security_path_mknod(&parent, dentry, mode, 0); - if (!err) { + if (!err) err = vfs_mknod(d_inode(parent.dentry), dentry, mode, 0); - if (!err) { - path.mnt = mntget(parent.mnt); - path.dentry = dget(dentry); - } - } - done_path_create(&parent, dentry); - if (err) + if (err) { + done_path_create(&parent, dentry); return err; - + } err = mutex_lock_interruptible(&u->bindlock); if (err) { - path_put(&path); + done_path_create(&parent, dentry); return err; } - if (u->addr) { mutex_unlock(&u->bindlock); - path_put(&path); + done_path_create(&parent, dentry); return -EINVAL; } addr->hash = UNIX_HASH_SIZE; - hash = d_backing_inode(path.dentry)->i_ino & (UNIX_HASH_SIZE - 1); + hash = d_backing_inode(dentry)->i_ino & (UNIX_HASH_SIZE - 1); spin_lock(&unix_table_lock); - u->path = path; + u->path.mnt = mntget(parent.mnt); + u->path.dentry = dget(dentry); __unix_set_addr(sk, addr, hash); spin_unlock(&unix_table_lock); mutex_unlock(&u->bindlock); + done_path_create(&parent, dentry); return 0; }
--
2.11.0