get_net_ns_by_fd() oopses if proc_ns_fget() returns an error

BTW, looking through the code related to struct net lifetime rules has
caught something else:

struct net *get_net_ns_by_fd(int fd)
{
        ...
        file = proc_ns_fget(fd);
        if (!file)
                goto out;

        ei = PROC_I(file->f_dentry->d_inode);

while in proc_ns_fget() we have two return ERR_PTR(...) and not a single
path that would return NULL.  The other caller of proc_ns_fget() treats
ERR_PTR() correctly...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 7 insertions, 9 deletions

diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index 6c6b86d0da15..e41e5110c65c 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -310,19 +310,17 @@ struct net *get_net_ns_by_fd(int fd)
         struct file *file;
         struct net *net;
 
-        net = ERR_PTR(-EINVAL);
         file = proc_ns_fget(fd);
-        if (!file)
-                goto out;
+        if (IS_ERR(file))
+                return ERR_CAST(file);
 
         ei = PROC_I(file->f_dentry->d_inode);
-        if (ei->ns_ops != &netns_operations)
-                goto out;
+        if (ei->ns_ops == &netns_operations)
+                net = get_net(ei->ns);
+        else
+                net = ERR_PTR(-EINVAL);
 
-        net = get_net(ei->ns);
-out:
-        if (file)
-                fput(file);
+        fput(file);
         return net;
 }