[RFC 1/1] net: fix rcu access on phonet_routes

[RFC 1/1] net: fix rcu access on phonet_routes

[Fabian Frederick]

-Add __rcu annotation on table to fix sparse warnings:
net/phonet/pn_dev.c:279:25: warning: incorrect type in assignment (different address spaces)
net/phonet/pn_dev.c:279:25:    expected struct net_device *<noident>
net/phonet/pn_dev.c:279:25:    got void [noderef] <asn:4>*<noident>
net/phonet/pn_dev.c:376:17: warning: incorrect type in assignment (different address spaces)
net/phonet/pn_dev.c:376:17:    expected struct net_device *volatile <noident>
net/phonet/pn_dev.c:376:17:    got struct net_device [noderef] <asn:4>*<noident>
net/phonet/pn_dev.c:392:17: warning: incorrect type in assignment (different address spaces)
net/phonet/pn_dev.c:392:17:    expected struct net_device *<noident>
net/phonet/pn_dev.c:392:17:    got void [noderef] <asn:4>*<noident>

-Access table with rcu_dereference (fixes the following sparse errors):
net/phonet/pn_dev.c:278:25: error: incompatible types in comparison expression (different address spaces)
net/phonet/pn_dev.c:391:17: error: incompatible types in comparison expression (different address spaces)

Signed-off-by: Fabian Frederick <fabf@skynet.be>
---
 net/phonet/pn_dev.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c
index 56a6146..5c9c0b2f1 100644
--- a/net/phonet/pn_dev.c
+++ b/net/phonet/pn_dev.c
@@ -36,7 +36,7 @@
 
 struct phonet_routes {
 	struct mutex		lock;
-	struct net_device	*table[64];
+	struct net_device __rcu	*table[64];
 };
 
 struct phonet_net {
@@ -275,7 +275,7 @@ static void phonet_route_autodel(struct net_device *dev)
 	bitmap_zero(deleted, 64);
 	mutex_lock(&pnn->routes.lock);
 	for (i = 0; i < 64; i++)
-		if (dev == pnn->routes.table[i]) {
+		if (rcu_dereference(pnn->routes.table[i]) == dev) {
 			RCU_INIT_POINTER(pnn->routes.table[i], NULL);
 			set_bit(i, deleted);
 		}
@@ -388,7 +388,7 @@ int phonet_route_del(struct net_device *dev, u8 daddr)
 
 	daddr = daddr >> 2;
 	mutex_lock(&routes->lock);
-	if (dev == routes->table[daddr])
+	if (rcu_dereference(routes->table[daddr]) == dev)
 		RCU_INIT_POINTER(routes->table[daddr], NULL);
 	else
 		dev = NULL;
-- 
1.9.3

Re: [RFC 1/1] net: fix rcu access on phonet_routes

[Rémi Denis-Courmont]

Le samedi 4 octobre 2014, 11:57:56 Fabian Frederick a écrit :
(snip)
> -Access table with rcu_dereference (fixes the following sparse errors):
> net/phonet/pn_dev.c:278:25: error: incompatible types in comparison
> expression (different address spaces) net/phonet/pn_dev.c:391:17: error:
> incompatible types in comparison expression (different address spaces)

Acked-by: Rémi Denis-Courmont <remi@remlab.net>

-- 
Rémi Denis-Courmont
http://www.remlab.net/

Re: [RFC 1/1] net: fix rcu access on phonet_routes

[Eric Dumazet]

On Sat, 2014-10-04 at 11:57 +0200, Fabian Frederick wrote:
> -Add __rcu annotation on table to fix sparse warnings:
> net/phonet/pn_dev.c:279:25: warning: incorrect type in assignment (different address spaces)
> net/phonet/pn_dev.c:279:25:    expected struct net_device *<noident>
> net/phonet/pn_dev.c:279:25:    got void [noderef] <asn:4>*<noident>
> net/phonet/pn_dev.c:376:17: warning: incorrect type in assignment (different address spaces)
> net/phonet/pn_dev.c:376:17:    expected struct net_device *volatile <noident>
> net/phonet/pn_dev.c:376:17:    got struct net_device [noderef] <asn:4>*<noident>
> net/phonet/pn_dev.c:392:17: warning: incorrect type in assignment (different address spaces)
> net/phonet/pn_dev.c:392:17:    expected struct net_device *<noident>
> net/phonet/pn_dev.c:392:17:    got void [noderef] <asn:4>*<noident>
> 
> -Access table with rcu_dereference (fixes the following sparse errors):
> net/phonet/pn_dev.c:278:25: error: incompatible types in comparison expression (different address spaces)
> net/phonet/pn_dev.c:391:17: error: incompatible types in comparison expression (different address spaces)
> 
> Signed-off-by: Fabian Frederick <fabf@skynet.be>
> ---
>  net/phonet/pn_dev.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/net/phonet/pn_dev.c b/net/phonet/pn_dev.c
> index 56a6146..5c9c0b2f1 100644
> --- a/net/phonet/pn_dev.c
> +++ b/net/phonet/pn_dev.c
> @@ -36,7 +36,7 @@
>  
>  struct phonet_routes {
>  	struct mutex		lock;
> -	struct net_device	*table[64];
> +	struct net_device __rcu	*table[64];
>  };
>  
>  struct phonet_net {
> @@ -275,7 +275,7 @@ static void phonet_route_autodel(struct net_device *dev)
>  	bitmap_zero(deleted, 64);
>  	mutex_lock(&pnn->routes.lock);
>  	for (i = 0; i < 64; i++)
> -		if (dev == pnn->routes.table[i]) {
> +		if (rcu_dereference(pnn->routes.table[i]) == dev) {
>  			RCU_INIT_POINTER(pnn->routes.table[i], NULL);
>  			set_bit(i, deleted);
>  		}
> @@ -388,7 +388,7 @@ int phonet_route_del(struct net_device *dev, u8 daddr)
>  
>  	daddr = daddr >> 2;
>  	mutex_lock(&routes->lock);
> -	if (dev == routes->table[daddr])
> +	if (rcu_dereference(routes->table[daddr]) == dev)
>  		RCU_INIT_POINTER(routes->table[daddr], NULL);
>  	else
>  		dev = NULL;

Hi Fabian

Have you tested this running the kernel with following config options :

CONFIG_LOCKDEP=y
CONFIG_PROVE_RCU=y

LOCKDEP should complain loudly, if not, we should file a bug !

Hint : Use rcu_access_pointer(), and check that LOCKDEP is happy with
that.

Thanks !