[RFC 05/12] xdp: allow attaching programs loaded for specific device

[Jakub Kicinski]

Pass the netdev pointer to bpf_prog_get_type().  This way
BPF code can decide whether the device matches what the
code was loaded/translated for.

Signed-off-by: Jakub Kicinski <jakub.kicin...@netronome.com>
Reviewed-by: Simon Horman <simon.hor...@netronome.com>
Reviewed-by: Quentin Monnet <quentin.mon...@netronome.com>
---
 include/linux/bpf.h  | 10 ++++++++++
 kernel/bpf/syscall.c | 33 +++++++++++++++++++++++++++++----
 net/core/dev.c       |  6 +++++-
 3 files changed, 44 insertions(+), 5 deletions(-)

diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 98bacd0fa5cc..c397934f91dd 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -335,6 +335,8 @@ extern const struct bpf_verifier_ops xdp_analyzer_ops;
 
 struct bpf_prog *bpf_prog_get(u32 ufd);
 struct bpf_prog *bpf_prog_get_type(u32 ufd, enum bpf_prog_type type);
+struct bpf_prog *bpf_prog_get_type_dev(u32 ufd, enum bpf_prog_type type,
+                                      struct net_device *netdev);
 struct bpf_prog * __must_check bpf_prog_add(struct bpf_prog *prog, int i);
 void bpf_prog_sub(struct bpf_prog *prog, int i);
 struct bpf_prog * __must_check bpf_prog_inc(struct bpf_prog *prog);
@@ -428,6 +430,14 @@ static inline struct bpf_prog *bpf_prog_get_type(u32 ufd,
 {
        return ERR_PTR(-EOPNOTSUPP);
 }
+
+static inline struct bpf_prog *bpf_prog_get_type_dev(u32 ufd,
+                                                    enum bpf_prog_type type,
+                                                    struct net_device *netdev)
+{
+       return ERR_PTR(-EOPNOTSUPP);
+}
+
 static inline struct bpf_prog * __must_check bpf_prog_add(struct bpf_prog 
*prog,
                                                          int i)
 {
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6712df2aa057..8c988025c8d3 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -1057,7 +1057,22 @@ struct bpf_prog *bpf_prog_inc_not_zero(struct bpf_prog 
*prog)
 }
 EXPORT_SYMBOL_GPL(bpf_prog_inc_not_zero);
 
-static struct bpf_prog *__bpf_prog_get(u32 ufd, enum bpf_prog_type 
*attach_type)
+static bool bpf_prog_can_attach(struct bpf_prog *prog,
+                               enum bpf_prog_type *attach_type,
+                               struct net_device *netdev)
+{
+       struct bpf_dev_offload *offload = prog->aux->offload;
+
+       if (prog->type != *attach_type)
+               return false;
+       if (offload && offload->netdev != netdev)
+               return false;
+
+       return true;
+}
+
+static struct bpf_prog *__bpf_prog_get(u32 ufd, enum bpf_prog_type 
*attach_type,
+                                      struct net_device *netdev)
 {
        struct fd f = fdget(ufd);
        struct bpf_prog *prog;
@@ -1065,7 +1080,7 @@ static struct bpf_prog *__bpf_prog_get(u32 ufd, enum 
bpf_prog_type *attach_type)
        prog = ____bpf_prog_get(f);
        if (IS_ERR(prog))
                return prog;
-       if (attach_type && (prog->type != *attach_type || prog->aux->offload)) {
+       if (attach_type && !bpf_prog_can_attach(prog, attach_type, netdev)) {
                prog = ERR_PTR(-EINVAL);
                goto out;
        }
@@ -1078,12 +1093,12 @@ static struct bpf_prog *__bpf_prog_get(u32 ufd, enum 
bpf_prog_type *attach_type)
 
 struct bpf_prog *bpf_prog_get(u32 ufd)
 {
-       return __bpf_prog_get(ufd, NULL);
+       return __bpf_prog_get(ufd, NULL, NULL);
 }
 
 struct bpf_prog *bpf_prog_get_type(u32 ufd, enum bpf_prog_type type)
 {
-       struct bpf_prog *prog = __bpf_prog_get(ufd, &type);
+       struct bpf_prog *prog = __bpf_prog_get(ufd, &type, NULL);
 
        if (!IS_ERR(prog))
                trace_bpf_prog_get_type(prog);
@@ -1091,6 +1106,16 @@ struct bpf_prog *bpf_prog_get_type(u32 ufd, enum 
bpf_prog_type type)
 }
 EXPORT_SYMBOL_GPL(bpf_prog_get_type);
 
+struct bpf_prog *bpf_prog_get_type_dev(u32 ufd, enum bpf_prog_type type,
+                                      struct net_device *netdev)
+{
+       struct bpf_prog *prog = __bpf_prog_get(ufd, &type, netdev);
+
+       if (!IS_ERR(prog))
+               trace_bpf_prog_get_type(prog);
+       return prog;
+}
+
 /* last field in 'union bpf_attr' used by this command */
 #define        BPF_PROG_LOAD_LAST_FIELD prog_ifindex
 
diff --git a/net/core/dev.c b/net/core/dev.c
index abed566e1b1d..9d84650598e0 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -7156,7 +7156,11 @@ int dev_change_xdp_fd(struct net_device *dev, struct 
netlink_ext_ack *extack,
                    __dev_xdp_attached(dev, bpf_op, NULL))
                        return -EBUSY;
 
-               prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_XDP);
+               if (bpf_op == ops->ndo_bpf)
+                       prog = bpf_prog_get_type_dev(fd, BPF_PROG_TYPE_XDP,
+                                                    dev);
+               else
+                       prog = bpf_prog_get_type(fd, BPF_PROG_TYPE_XDP);
                if (IS_ERR(prog))
                        return PTR_ERR(prog);
        }
-- 
2.14.1