[PATCH 3.10 135/268] af_unix: move unix_mknod() out of bindlock
From: Willy Tarreau <w@1wt.eu>
Date: 2017-06-19 19:21:30
Also in:
lkml
Subsystem:
networking [general], networking [unix sockets], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Kuniyuki Iwashima, Linus Torvalds
From: WANG Cong <redacted> commit 0fb44559ffd67de8517098b81f675fa0210f13f0 upstream. 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: Dmitry Vyukov <dvyukov@google.com> Tested-by: Dmitry Vyukov <dvyukov@google.com> Cc: Rainer Weikusat <redacted> Cc: Al Viro <viro@zeniv.linux.org.uk> Signed-off-by: Cong Wang <redacted> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Willy Tarreau <w@1wt.eu> --- net/unix/af_unix.c | 27 ++++++++++++++++----------- 1 file changed, 16 insertions(+), 11 deletions(-)
diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 8f118c7..4b18115 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c@@ -977,6 +977,7 @@ 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)
@@ -992,9 +993,20 @@ 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->readlock); if (err) - goto out; + goto out_put; err = -EINVAL; if (u->addr)
@@ -1011,16 +1023,6 @@ 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 = path.dentry->d_inode->i_ino & (UNIX_HASH_SIZE-1); spin_lock(&unix_table_lock);
@@ -1047,6 +1049,9 @@ out_unlock: spin_unlock(&unix_table_lock); out_up: mutex_unlock(&u->readlock); +out_put: + if (err) + path_put(&path); out: return err; }
--
2.8.0.rc2.1.gbe9624a