From: =?UTF-8?q?Toke=20H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
Date: Thu, 24 Jun 2021 18:05:57 +0200
Subject: ena: Remove rcu_read_lock() around XDP program invocation
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Patch-mainline: v5.14-rc1
Git-commit: 0939e0537896e421e391fa4b1a0b052907808e0d
References: bsc#1197099 jsc#SLE-24125

The ena driver has rcu_read_lock()/rcu_read_unlock() pairs around XDP
program invocations. However, the actual lifetime of the objects referred
by the XDP program invocation is longer, all the way through to the call to
xdp_do_flush(), making the scope of the rcu_read_lock() too small. This
turns out to be harmless because it all happens in a single NAPI poll
cycle (and thus under local_bh_disable()), but it makes the rcu_read_lock()
misleading.

Rather than extend the scope of the rcu_read_lock(), just get rid of it
entirely. With the addition of RCU annotations to the XDP_REDIRECT map
types that take bh execution into account, lockdep even understands this to
be safe, so there's really no reason to keep it around.

Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Saeed Bishara <saeedb@amazon.com>
Cc: Guy Tzalik <gtzalik@amazon.com>
Link: https://lore.kernel.org/bpf/20210624160609.292325-8-toke@redhat.com
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/ethernet/amazon/ena/ena_netdev.c |    3 ---
 1 file changed, 3 deletions(-)

--- a/drivers/net/ethernet/amazon/ena/ena_netdev.c
+++ b/drivers/net/ethernet/amazon/ena/ena_netdev.c
@@ -393,7 +393,6 @@ static int ena_xdp_execute(struct ena_ri
 	struct xdp_frame *xdpf;
 	u64 *xdp_stat;
 
-	rcu_read_lock();
 	xdp_prog = READ_ONCE(rx_ring->xdp_bpf_prog);
 
 	if (!xdp_prog)
@@ -448,8 +447,6 @@ static int ena_xdp_execute(struct ena_ri
 
 	ena_increase_stat(xdp_stat, 1, &rx_ring->syncp);
 out:
-	rcu_read_unlock();
-
 	return verdict;
 }