[PATCH v2] net/af_unix: don't create a path for a binded socket

[Denis Kirjanov]

in the case of the socket which is bound to an adress
there is no sense to create a path in the next attempts

here is a program that shows the issue:

int main()
{
    int s;
    struct sockaddr_un a;

    s = socket(AF_UNIX, SOCK_STREAM, 0);
    if (s<0)
        perror("socket() failed\n");

    printf("First bind()\n");

    memset(&a, 0, sizeof(a));
    a.sun_family = AF_UNIX;
    strncpy(a.sun_path, "/tmp/.first_bind", sizeof(a.sun_path));

    if ((bind(s, (const struct sockaddr*) &a, sizeof(a))) == -1)
        perror("bind() failed\n");

    printf("Second bind()\n");

    memset(&a, 0, sizeof(a));
    a.sun_family = AF_UNIX;
    strncpy(a.sun_path, "/tmp/.first_bind_failed", sizeof(a.sun_path));

    if ((bind(s, (const struct sockaddr*) &a, sizeof(a))) == -1)
        perror("bind() failed\n");
}

kda@SLES15-SP2:~> ./test
First bind()
Second bind()
bind() failed
: Invalid argument

kda@SLES15-SP2:~> ls -la /tmp/.first_bind
.first_bind         .first_bind_failed

Signed-off-by: Denis Kirjanov <k...@linux-powerpc.org>

v2: move a new patch creation after the address assignment check.
---
 net/unix/af_unix.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 41c3303c3357..ff2dd1d3536b 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1034,6 +1034,14 @@ static int unix_bind(struct socket *sock, struct 
sockaddr *uaddr, int addr_len)
                goto out;
        addr_len = err;
 
+       err = mutex_lock_interruptible(&u->bindlock);
+       if (err)
+               goto out_put;
+
+       err = -EINVAL;
+       if (u->addr)
+               goto out_up;
+
        if (sun_path[0]) {
                umode_t mode = S_IFSOCK |
                       (SOCK_INODE(sock)->i_mode & ~current_umask());
@@ -1045,14 +1053,6 @@ static int unix_bind(struct socket *sock, struct 
sockaddr *uaddr, int addr_len)
                }
        }
 
-       err = mutex_lock_interruptible(&u->bindlock);
-       if (err)
-               goto out_put;
-
-       err = -EINVAL;
-       if (u->addr)
-               goto out_up;
-
        err = -ENOMEM;
        addr = kmalloc(sizeof(*addr)+addr_len, GFP_KERNEL);
        if (!addr)
-- 
2.16.4