diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2020-02-24 15:01:48 +0100 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-02-24 16:20:10 -0800 |
| commit | 085fee1a72a9fba101a4a68a2c02fa8bd2b6f913 (patch) | |
| tree | e215f625f6ca1185cd82d9fd65a2585c109f6b5d | |
| parent | c518cfa0c5ad75ddf3d743f1e35b9cf5fc2c346e (diff) | |
bpf: Use recursion prevention helpers in hashtab code
The required protection is that the caller cannot be migrated to a
different CPU as these places take either a hash bucket lock or might
trigger a kprobe inside the memory allocator. Both scenarios can lead to
deadlocks. The deadlock prevention is per CPU by incrementing a per CPU
variable which temporarily blocks the invocation of BPF programs from perf
and kprobes.
Replace the open coded preempt_disable/enable() and this_cpu_inc/dec()
pairs with the new recursion prevention helpers to prepare BPF to work on
PREEMPT_RT enabled kernels. On a non-RT kernel the migrate disable/enable
in the helpers map to preempt_disable/enable(), i.e. no functional change.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200224145644.211208533@linutronix.de
| -rw-r--r-- | kernel/bpf/hashtab.c | 12 |
1 files changed, 4 insertions, 8 deletions
diff --git a/kernel/bpf/hashtab.c b/kernel/bpf/hashtab.c index 431cef22d29d..ef83b012d8d8 100644 --- a/kernel/bpf/hashtab.c +++ b/kernel/bpf/hashtab.c @@ -1333,8 +1333,7 @@ alloc: } again: - preempt_disable(); - this_cpu_inc(bpf_prog_active); + bpf_disable_instrumentation(); rcu_read_lock(); again_nocopy: dst_key = keys; @@ -1362,8 +1361,7 @@ again_nocopy: */ raw_spin_unlock_irqrestore(&b->lock, flags); rcu_read_unlock(); - this_cpu_dec(bpf_prog_active); - preempt_enable(); + bpf_enable_instrumentation(); goto after_loop; } @@ -1374,8 +1372,7 @@ again_nocopy: */ raw_spin_unlock_irqrestore(&b->lock, flags); rcu_read_unlock(); - this_cpu_dec(bpf_prog_active); - preempt_enable(); + bpf_enable_instrumentation(); kvfree(keys); kvfree(values); goto alloc; @@ -1445,8 +1442,7 @@ next_batch: } rcu_read_unlock(); - this_cpu_dec(bpf_prog_active); - preempt_enable(); + bpf_enable_instrumentation(); if (bucket_cnt && (copy_to_user(ukeys + total * key_size, keys, key_size * bucket_cnt) || copy_to_user(uvalues + total * value_size, values, |