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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: Dmitry Vyukov <dvyukov@google.com>
Tested-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Rainer Weikusat <rweikusat@mobileactivedefense.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>
This commit is contained in:
WANG Cong 2017-01-23 11:17:35 -08:00 committed by David S. Miller
parent a59b7e0246
commit 0fb44559ff
1 changed files with 16 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

27
net/unix/af_unix.c
View File

@ -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;
}