From: Jakub Kicinski <jakub.kicinski@netronome.com>
Date: Thu, 31 Oct 2019 20:07:00 -0700
Subject: net: fix installing orphaned programs
Patch-mainline: v5.4-rc6
Git-commit: aefc3e723a78c2e429a64dadd7815ef2a4aecd44
References: bsc#1154353

When netdevice with offloaded BPF programs is destroyed
the programs are orphaned and removed from the program
IDA - their IDs get released (the programs may remain
accessible via existing open file descriptors and pinned
files). After IDs are released they are set to 0.

This confuses dev_change_xdp_fd() because it compares
the __dev_xdp_query() result where 0 means no program
with prog->aux->id where 0 means orphaned.

dev_change_xdp_fd() would have incorrectly returned success
even though it had not installed the program.

Since drivers already catch this case via bpf_offload_dev_match()
let them handle this case. The error message drivers produce in
this case ("program loaded for a different device") is in fact
correct as the orphaned program must had to be loaded for a
different device.

Fixes: c14a9f633d9e ("net: Don't call XDP_SETUP_PROG when nothing is changed")
Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 net/core/dev.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -8421,7 +8421,8 @@ int dev_change_xdp_fd(struct net_device
 			return -EINVAL;
 		}
 
-		if (prog->aux->id == prog_id) {
+		/* prog->aux->id may be 0 for orphaned device-bound progs */
+		if (prog->aux->id && prog->aux->id == prog_id) {
 			bpf_prog_put(prog);
 			return 0;
 		}