[PATCH 6.1 051/127] bpf: sockmap: Remove preempt_disable in sock_map_sk_acquire

Greg Kroah-Hartman
2023-08-09T10:53:33Z

From: Tomas Glozar <tglozar@redhat.com>

[ Upstream commit 13d2618b48f15966d1adfe1ff6a1985f5eef40ba ]

Disabling preemption in sock_map_sk_acquire conflicts with GFP_ATOMIC
allocation later in sk_psock_init_link on PREEMPT_RT kernels, since
GFP_ATOMIC might sleep on RT (see bpf: Make BPF and PREEMPT_RT co-exist
patchset notes for details).

This causes calling bpf_map_update_elem on BPF_MAP_TYPE_SOCKMAP maps to
BUG (sleeping function called from invalid context) on RT kernels.

preempt_disable was introduced together with lock_sk and rcu_read_lock
in commit 99ba2b5aba24e ("bpf: sockhash, disallow bpf_tcp_close and update
in parallel"), probably to match disabled migration of BPF programs, and
is no longer necessary.

Remove preempt_disable to fix BUG in sock_map_update_common on RT.

Signed-off-by: Tomas Glozar <tglozar@redhat.com>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/all/20200224140131.461979697@linutronix.de/
Fixes: 99ba2b5aba24 ("bpf: sockhash, disallow bpf_tcp_close and update in parallel")
Reviewed-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/r/20230728064411.305576-1-tglozar@redhat.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
net/core/sock_map.c | 2 --
1 file changed, 2 deletions(-)

diff --git a/net/core/sock_map.c b/net/core/sock_map.c
index d382672018928..c84e5073c0b66 100644
--- a/net/core/sock_map.c
+++ b/net/core/sock_map.c
@@ -117,7 +117,6 @@ static void sock_map_sk_acquire(struct sock *sk)
__acquires(&sk->sk_lock.slock)
{
lock_sock(sk);
- preempt_disable();
rcu_read_lock();
}

@@ -125,7 +124,6 @@ static void sock_map_sk_release(struct sock *sk)
__releases(&sk->sk_lock.slock)
{
rcu_read_unlock();
- preempt_enable();
release_sock(sk);
}

--
2.40.1