net: netprio: fix files lock and remove useless d_path bits

Add lock to prevent a race with a file closing and also remove
useless and ugly sscanf code. The extra code was never needed
and the case it supposedly protected against is in fact handled
correctly by sock_from_file as pointed out by Al Viro.

CC: Neil Horman <nhorman@tuxdriver.com>
Reported-by: Al Viro <viro@ZenIV.linux.org.uk>
Signed-off-by: John Fastabend <john.r.fastabend@intel.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 18 deletions

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index ed0c0431fcd8..f65dba3afd99 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -277,12 +277,6 @@ out_free_devname:
 void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
 {
         struct task_struct *p;
-        char *tmp = kzalloc(sizeof(char) * PATH_MAX, GFP_KERNEL);
-
-        if (!tmp) {
-                pr_warn("Unable to attach cgrp due to alloc failure!\n");
-                return;
-        }
 
         cgroup_taskset_for_each(p, cgrp, tset) {
                 unsigned int fd;
@@ -296,32 +290,24 @@ void net_prio_attach(struct cgroup *cgrp, struct cgroup_taskset *tset)
                         continue;
                 }
 
-                rcu_read_lock();
+                spin_lock(&files->file_lock);
                 fdt = files_fdtable(files);
                 for (fd = 0; fd < fdt->max_fds; fd++) {
-                        char *path;
                         struct file *file;
                         struct socket *sock;
-                        unsigned long s;
-                        int rv, err = 0;
+                        int err;
 
                         file = fcheck_files(files, fd);
                         if (!file)
                                 continue;
 
-                        path = d_path(&file->f_path, tmp, PAGE_SIZE);
-                        rv = sscanf(path, "socket:[%lu]", &s);
-                        if (rv <= 0)
-                                continue;
-
                         sock = sock_from_file(file, &err);
-                        if (!err)
+                        if (sock)
                                 sock_update_netprioidx(sock->sk, p);
                 }
-                rcu_read_unlock();
+                spin_unlock(&files->file_lock);
                 task_unlock(p);
         }
-        kfree(tmp);
 }
 
 static struct cftype ss_files[] = {