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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Thu, 26 Oct 2023 15:17:32 +0200
Subject: [PATCH 13/15] net: Use nested-BH locking for bpf_scratchpad.
Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.10/older/patches-6.10.2-rt14.tar.xz
bpf_scratchpad is a per-CPU variable and relies on disabled BH for its
locking. Without per-CPU locking in local_bh_disable() on PREEMPT_RT
this data structure requires explicit locking.
Add a local_lock_t to the data structure and use local_lock_nested_bh()
for locking. This change adds only lockdep coverage and does not alter
the functional behaviour for !PREEMPT_RT.
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Hao Luo <haoluo@google.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Yonghong Song <yonghong.song@linux.dev>
Cc: bpf@vger.kernel.org
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
net/core/filter.c | 11 +++++++++--
1 file changed, 9 insertions(+), 2 deletions(-)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -1658,9 +1658,12 @@ struct bpf_scratchpad {
__be32 diff[MAX_BPF_STACK / sizeof(__be32)];
u8 buff[MAX_BPF_STACK];
};
+ local_lock_t bh_lock;
};
-static DEFINE_PER_CPU(struct bpf_scratchpad, bpf_sp);
+static DEFINE_PER_CPU(struct bpf_scratchpad, bpf_sp) = {
+ .bh_lock = INIT_LOCAL_LOCK(bh_lock),
+};
static inline int __bpf_try_make_writable(struct sk_buff *skb,
unsigned int write_len)
@@ -2021,6 +2024,7 @@ BPF_CALL_5(bpf_csum_diff, __be32 *, from
struct bpf_scratchpad *sp = this_cpu_ptr(&bpf_sp);
u32 diff_size = from_size + to_size;
int i, j = 0;
+ __wsum ret;
/* This is quite flexible, some examples:
*
@@ -2034,12 +2038,15 @@ BPF_CALL_5(bpf_csum_diff, __be32 *, from
diff_size > sizeof(sp->diff)))
return -EINVAL;
+ local_lock_nested_bh(&bpf_sp.bh_lock);
for (i = 0; i < from_size / sizeof(__be32); i++, j++)
sp->diff[j] = ~from[i];
for (i = 0; i < to_size / sizeof(__be32); i++, j++)
sp->diff[j] = to[i];
- return csum_partial(sp->diff, diff_size, seed);
+ ret = csum_partial(sp->diff, diff_size, seed);
+ local_unlock_nested_bh(&bpf_sp.bh_lock);
+ return ret;
}
static const struct bpf_func_proto bpf_csum_diff_proto = {
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