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@xxxxxxxxxx>
Cc: Andrii Nakryiko <andrii@xxxxxxxxxx>
Cc: Hao Luo <haoluo@xxxxxxxxxx>
Cc: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: John Fastabend <john.fastabend@xxxxxxxxx>
Cc: KP Singh <kpsingh@xxxxxxxxxx>
Cc: Martin KaFai Lau <martin.lau@xxxxxxxxx>
Cc: Song Liu <song@xxxxxxxxxx>
Cc: Stanislav Fomichev <sdf@xxxxxxxxxx>
Cc: Yonghong Song <yonghong.song@xxxxxxxxx>
Cc: bpf@xxxxxxxxxxxxxxx
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
net/core/filter.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)
diff --git a/net/core/filter.c b/net/core/filter.c
index cfe8ea59fd9db..e95b235a1e4f4 100644
--- 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)
@@ -2029,6 +2032,7 @@ BPF_CALL_5(bpf_csum_diff, __be32 *, from, u32, from_size,
diff_size > sizeof(sp->diff)))
return -EINVAL;
+ guard(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++)
--
2.43.0
