devlink: Fix list access without lock while reading region

While finding the devlink device during region reading,
devlink device list is accessed and devlink device is
returned without holding a lock. This could lead to use-after-free
accesses.

While at it, add lockdep assert to ensure that all future callers hold
the lock when calling devlink_get_from_attrs().

Fixes: 4e54795a27f5 ("devlink: Add support for region snapshot read command")
Signed-off-by: Parav Pandit <parav@mellanox.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/core/devlink.c b/net/core/devlink.c
index 312084f76a0ac1949ee0c62af9b160b80d48f579..1d7502a5a651d98fdfd2c4ee7cc36a09b7e313b7 100644 (file)
--- a/net/core/devlink.c
+++ b/net/core/devlink.c
@@ -116,6 +116,8 @@ static struct devlink *devlink_get_from_attrs(struct net *net,
        busname = nla_data(attrs[DEVLINK_ATTR_BUS_NAME]);
        devname = nla_data(attrs[DEVLINK_ATTR_DEV_NAME]);
 
+       lockdep_assert_held(&devlink_mutex);
+
        list_for_each_entry(devlink, &devlink_list, list) {
                if (strcmp(devlink->dev->bus->name, busname) == 0 &&
                    strcmp(dev_name(devlink->dev), devname) == 0 &&
@@ -3645,13 +3647,13 @@ static int devlink_nl_cmd_region_read_dumpit(struct sk_buff *skb,
        if (err)
                goto out_free;
 
+       mutex_lock(&devlink_mutex);
        devlink = devlink_get_from_attrs(sock_net(cb->skb->sk), attrs);
        if (IS_ERR(devlink)) {
                err = PTR_ERR(devlink);
-               goto out_free;
+               goto out_dev;
        }
 
-       mutex_lock(&devlink_mutex);
        mutex_lock(&devlink->lock);
 
        if (!attrs[DEVLINK_ATTR_REGION_NAME] ||
@@ -3729,6 +3731,7 @@ nla_put_failure:
        genlmsg_cancel(skb, hdr);
 out_unlock:
        mutex_unlock(&devlink->lock);
+out_dev:
        mutex_unlock(&devlink_mutex);
 out_free:
        kfree(attrs);