diff mbox series

[v2,bpf-next,1/5] devmap: Formalize map value as a named struct

Message ID 20200528001423.58575-2-dsahern@kernel.org
State Changes Requested
Delegated to: BPF Maintainers
Headers show
Series bpf: Add support for XDP programs in DEVMAP entries | expand

Commit Message

David Ahern May 28, 2020, 12:14 a.m. UTC 
From: David Ahern <dsahern@gmail.com>

Add 'struct devmap_val' to the bpf uapi to formalize the
expected values that can be passed in for a DEVMAP.
Update devmap code to use the struct.

Signed-off-by: David Ahern <dsahern@gmail.com>
---
 include/uapi/linux/bpf.h       |  5 ++++
 kernel/bpf/devmap.c            | 43 ++++++++++++++++++++--------------
 tools/include/uapi/linux/bpf.h |  5 ++++
 3 files changed, 35 insertions(+), 18 deletions(-)

Comments

Andrii Nakryiko May 28, 2020, 7:01 a.m. UTC | #1 
On Wed, May 27, 2020 at 5:15 PM David Ahern <dsahern@kernel.org> wrote:
>
> From: David Ahern <dsahern@gmail.com>
>
> Add 'struct devmap_val' to the bpf uapi to formalize the
> expected values that can be passed in for a DEVMAP.
> Update devmap code to use the struct.
>
> Signed-off-by: David Ahern <dsahern@gmail.com>
> ---
>  include/uapi/linux/bpf.h       |  5 ++++
>  kernel/bpf/devmap.c            | 43 ++++++++++++++++++++--------------
>  tools/include/uapi/linux/bpf.h |  5 ++++
>  3 files changed, 35 insertions(+), 18 deletions(-)
>
> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> index 54b93f8b49b8..d27302ecaa9c 100644
> --- a/include/uapi/linux/bpf.h
> +++ b/include/uapi/linux/bpf.h
> @@ -3625,6 +3625,11 @@ struct xdp_md {
>         __u32 rx_queue_index;  /* rxq->queue_index  */
>  };
>
> +/* DEVMAP values */
> +struct devmap_val {
> +       __u32 ifindex;   /* device index */
> +};
> +

can DEVMAP be used outside of BPF ecosystem? If not, shouldn't this be
`struct bpf_devmap_val`, to be consistent with the rest of the type
names?

>  enum sk_action {
>         SK_DROP = 0,
>         SK_PASS,
> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
> index a51d9fb7a359..069a50113e26 100644
> --- a/kernel/bpf/devmap.c
> +++ b/kernel/bpf/devmap.c
> @@ -66,6 +66,7 @@ struct bpf_dtab_netdev {
>         struct bpf_dtab *dtab;
>         struct rcu_head rcu;
>         unsigned int idx;
> +       struct devmap_val val;
>  };
>
>  struct bpf_dtab {
> @@ -110,7 +111,8 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
>
>         /* check sanity of attributes */
>         if (attr->max_entries == 0 || attr->key_size != 4 ||
> -           attr->value_size != 4 || attr->map_flags & ~DEV_CREATE_FLAG_MASK)
> +           attr->value_size > sizeof(struct devmap_val) ||

So is 0, 1, 2, 3, and after next patch 5, 6, and 7 all allowed as
well? Isn't that a bit too permissive?

> +           attr->map_flags & ~DEV_CREATE_FLAG_MASK)
>                 return -EINVAL;
>

[...]
David Ahern May 28, 2020, 10:37 p.m. UTC | #2 
On 5/28/20 1:01 AM, Andrii Nakryiko wrote:
> On Wed, May 27, 2020 at 5:15 PM David Ahern <dsahern@kernel.org> wrote:
>>
>> From: David Ahern <dsahern@gmail.com>
>>
>> Add 'struct devmap_val' to the bpf uapi to formalize the
>> expected values that can be passed in for a DEVMAP.
>> Update devmap code to use the struct.
>>
>> Signed-off-by: David Ahern <dsahern@gmail.com>
>> ---
>>  include/uapi/linux/bpf.h       |  5 ++++
>>  kernel/bpf/devmap.c            | 43 ++++++++++++++++++++--------------
>>  tools/include/uapi/linux/bpf.h |  5 ++++
>>  3 files changed, 35 insertions(+), 18 deletions(-)
>>
>> diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
>> index 54b93f8b49b8..d27302ecaa9c 100644
>> --- a/include/uapi/linux/bpf.h
>> +++ b/include/uapi/linux/bpf.h
>> @@ -3625,6 +3625,11 @@ struct xdp_md {
>>         __u32 rx_queue_index;  /* rxq->queue_index  */
>>  };
>>
>> +/* DEVMAP values */
>> +struct devmap_val {
>> +       __u32 ifindex;   /* device index */
>> +};
>> +
> 
> can DEVMAP be used outside of BPF ecosystem? If not, shouldn't this be
> `struct bpf_devmap_val`, to be consistent with the rest of the type
> names?

sure, added 'bpf_' to the name.

> 
>>  enum sk_action {
>>         SK_DROP = 0,
>>         SK_PASS,
>> diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
>> index a51d9fb7a359..069a50113e26 100644
>> --- a/kernel/bpf/devmap.c
>> +++ b/kernel/bpf/devmap.c
>> @@ -66,6 +66,7 @@ struct bpf_dtab_netdev {
>>         struct bpf_dtab *dtab;
>>         struct rcu_head rcu;
>>         unsigned int idx;
>> +       struct devmap_val val;
>>  };
>>
>>  struct bpf_dtab {
>> @@ -110,7 +111,8 @@ static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
>>
>>         /* check sanity of attributes */
>>         if (attr->max_entries == 0 || attr->key_size != 4 ||
>> -           attr->value_size != 4 || attr->map_flags & ~DEV_CREATE_FLAG_MASK)
>> +           attr->value_size > sizeof(struct devmap_val) ||
> 
> So is 0, 1, 2, 3, and after next patch 5, 6, and 7 all allowed as
> well? Isn't that a bit too permissive?

sure, I should check that it is at least 4-bytes - the existing size of
the values. After that the struct can vary as user and kernel differ.
The key is that newer userspace can not send down a higher value size
than the kernel supports  and older userspace can send fewer bytes
(e.g., 4-byte ifindex only vs 8-byte ifindex + fd). I'll revert this to
v1 where I check for specific known value sizes.

> 
>> +           attr->map_flags & ~DEV_CREATE_FLAG_MASK)
>>                 return -EINVAL;
>>
> 
> [...]
>
diff mbox series

Patch

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 54b93f8b49b8..d27302ecaa9c 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -3625,6 +3625,11 @@  struct xdp_md {
 	__u32 rx_queue_index;  /* rxq->queue_index  */
 };
 
+/* DEVMAP values */
+struct devmap_val {
+	__u32 ifindex;   /* device index */
+};
+
 enum sk_action {
 	SK_DROP = 0,
 	SK_PASS,
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index a51d9fb7a359..069a50113e26 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -66,6 +66,7 @@  struct bpf_dtab_netdev {
 	struct bpf_dtab *dtab;
 	struct rcu_head rcu;
 	unsigned int idx;
+	struct devmap_val val;
 };
 
 struct bpf_dtab {
@@ -110,7 +111,8 @@  static int dev_map_init_map(struct bpf_dtab *dtab, union bpf_attr *attr)
 
 	/* check sanity of attributes */
 	if (attr->max_entries == 0 || attr->key_size != 4 ||
-	    attr->value_size != 4 || attr->map_flags & ~DEV_CREATE_FLAG_MASK)
+	    attr->value_size > sizeof(struct devmap_val) ||
+	    attr->map_flags & ~DEV_CREATE_FLAG_MASK)
 		return -EINVAL;
 
 	/* Lookup returns a pointer straight to dev->ifindex, so make sure the
@@ -472,18 +474,15 @@  int dev_map_generic_redirect(struct bpf_dtab_netdev *dst, struct sk_buff *skb,
 static void *dev_map_lookup_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_dtab_netdev *obj = __dev_map_lookup_elem(map, *(u32 *)key);
-	struct net_device *dev = obj ? obj->dev : NULL;
 
-	return dev ? &dev->ifindex : NULL;
+	return obj ? &obj->val : NULL;
 }
 
 static void *dev_map_hash_lookup_elem(struct bpf_map *map, void *key)
 {
 	struct bpf_dtab_netdev *obj = __dev_map_hash_lookup_elem(map,
 								*(u32 *)key);
-	struct net_device *dev = obj ? obj->dev : NULL;
-
-	return dev ? &dev->ifindex : NULL;
+	return obj ? &obj->val : NULL;
 }
 
 static void __dev_map_entry_free(struct rcu_head *rcu)
@@ -541,7 +540,7 @@  static int dev_map_hash_delete_elem(struct bpf_map *map, void *key)
 
 static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
 						    struct bpf_dtab *dtab,
-						    u32 ifindex,
+						    struct devmap_val *val,
 						    unsigned int idx)
 {
 	struct bpf_dtab_netdev *dev;
@@ -551,16 +550,18 @@  static struct bpf_dtab_netdev *__dev_map_alloc_node(struct net *net,
 	if (!dev)
 		return ERR_PTR(-ENOMEM);
 
-	dev->dev = dev_get_by_index(net, ifindex);
-	if (!dev->dev) {
-		kfree(dev);
-		return ERR_PTR(-EINVAL);
-	}
+	dev->dev = dev_get_by_index(net, val->ifindex);
+	if (!dev->dev)
+		goto err_out;
 
 	dev->idx = idx;
 	dev->dtab = dtab;
+	dev->val.ifindex = val->ifindex;
 
 	return dev;
+err_out:
+	kfree(dev);
+	return ERR_PTR(-EINVAL);
 }
 
 static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
@@ -568,7 +569,7 @@  static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
 {
 	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
 	struct bpf_dtab_netdev *dev, *old_dev;
-	u32 ifindex = *(u32 *)value;
+	struct devmap_val val = { };
 	u32 i = *(u32 *)key;
 
 	if (unlikely(map_flags > BPF_EXIST))
@@ -578,10 +579,13 @@  static int __dev_map_update_elem(struct net *net, struct bpf_map *map,
 	if (unlikely(map_flags == BPF_NOEXIST))
 		return -EEXIST;
 
-	if (!ifindex) {
+	/* already verified value_size <= sizeof val */
+	memcpy(&val, value, map->value_size);
+
+	if (!val.ifindex) {
 		dev = NULL;
 	} else {
-		dev = __dev_map_alloc_node(net, dtab, ifindex, i);
+		dev = __dev_map_alloc_node(net, dtab, &val, i);
 		if (IS_ERR(dev))
 			return PTR_ERR(dev);
 	}
@@ -609,12 +613,15 @@  static int __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
 {
 	struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
 	struct bpf_dtab_netdev *dev, *old_dev;
-	u32 ifindex = *(u32 *)value;
+	struct devmap_val val = { };
 	u32 idx = *(u32 *)key;
 	unsigned long flags;
 	int err = -EEXIST;
 
-	if (unlikely(map_flags > BPF_EXIST || !ifindex))
+	/* already verified value_size <= sizeof val */
+	memcpy(&val, value, map->value_size);
+
+	if (unlikely(map_flags > BPF_EXIST || !val.ifindex))
 		return -EINVAL;
 
 	spin_lock_irqsave(&dtab->index_lock, flags);
@@ -623,7 +630,7 @@  static int __dev_map_hash_update_elem(struct net *net, struct bpf_map *map,
 	if (old_dev && (map_flags & BPF_NOEXIST))
 		goto out_err;
 
-	dev = __dev_map_alloc_node(net, dtab, ifindex, idx);
+	dev = __dev_map_alloc_node(net, dtab, &val, idx);
 	if (IS_ERR(dev)) {
 		err = PTR_ERR(dev);
 		goto out_err;
diff --git a/tools/include/uapi/linux/bpf.h b/tools/include/uapi/linux/bpf.h
index 54b93f8b49b8..d27302ecaa9c 100644
--- a/tools/include/uapi/linux/bpf.h
+++ b/tools/include/uapi/linux/bpf.h
@@ -3625,6 +3625,11 @@  struct xdp_md {
 	__u32 rx_queue_index;  /* rxq->queue_index  */
 };
 
+/* DEVMAP values */
+struct devmap_val {
+	__u32 ifindex;   /* device index */
+};
+
 enum sk_action {
 	SK_DROP = 0,
 	SK_PASS,