diff options
| author | Thomas Gleixner <tglx@linutronix.de> | 2020-02-24 15:01:49 +0100 |
|---|---|---|
| committer | Alexei Starovoitov <ast@kernel.org> | 2020-02-24 16:20:10 -0800 |
| commit | b6e5dae15a61b0cc9219799926813baad0b58967 (patch) | |
| tree | 54d5a5804fe457956725474e079ec989054cba3c /kernel/bpf/syscall.c | |
| parent | 085fee1a72a9fba101a4a68a2c02fa8bd2b6f913 (diff) | |
bpf: Replace open coded recursion prevention in sys_bpf()
The required protection is that the caller cannot be migrated to a
different CPU as these functions end up in places which 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_[dis|en]able and __this_cpu_[inc|dec] pairs
with the new helper functions. These functions are already prepared to make
BPF work on PREEMPT_RT enabled kernels. No functional change for !RT
kernels.
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200224145644.317843926@linutronix.de
Diffstat (limited to 'kernel/bpf/syscall.c')
| -rw-r--r-- | kernel/bpf/syscall.c | 27 |
1 files changed, 8 insertions, 19 deletions
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c index a91ad518c050..a79743a89815 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -171,11 +171,7 @@ static int bpf_map_update_value(struct bpf_map *map, struct fd f, void *key, flags); } - /* must increment bpf_prog_active to avoid kprobe+bpf triggering from - * inside bpf map update or delete otherwise deadlocks are possible - */ - preempt_disable(); - __this_cpu_inc(bpf_prog_active); + bpf_disable_instrumentation(); if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH || map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) { err = bpf_percpu_hash_update(map, key, value, flags); @@ -206,8 +202,7 @@ static int bpf_map_update_value(struct bpf_map *map, struct fd f, void *key, err = map->ops->map_update_elem(map, key, value, flags); rcu_read_unlock(); } - __this_cpu_dec(bpf_prog_active); - preempt_enable(); + bpf_enable_instrumentation(); maybe_wait_bpf_programs(map); return err; @@ -222,8 +217,7 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value, if (bpf_map_is_dev_bound(map)) return bpf_map_offload_lookup_elem(map, key, value); - preempt_disable(); - this_cpu_inc(bpf_prog_active); + bpf_disable_instrumentation(); if (map->map_type == BPF_MAP_TYPE_PERCPU_HASH || map->map_type == BPF_MAP_TYPE_LRU_PERCPU_HASH) { err = bpf_percpu_hash_copy(map, key, value); @@ -268,8 +262,7 @@ static int bpf_map_copy_value(struct bpf_map *map, void *key, void *value, rcu_read_unlock(); } - this_cpu_dec(bpf_prog_active); - preempt_enable(); + bpf_enable_instrumentation(); maybe_wait_bpf_programs(map); return err; @@ -1136,13 +1129,11 @@ static int map_delete_elem(union bpf_attr *attr) goto out; } - preempt_disable(); - __this_cpu_inc(bpf_prog_active); + bpf_disable_instrumentation(); rcu_read_lock(); err = map->ops->map_delete_elem(map, key); rcu_read_unlock(); - __this_cpu_dec(bpf_prog_active); - preempt_enable(); + bpf_enable_instrumentation(); maybe_wait_bpf_programs(map); out: kfree(key); @@ -1254,13 +1245,11 @@ int generic_map_delete_batch(struct bpf_map *map, break; } - preempt_disable(); - __this_cpu_inc(bpf_prog_active); + bpf_disable_instrumentation(); rcu_read_lock(); err = map->ops->map_delete_elem(map, key); rcu_read_unlock(); - __this_cpu_dec(bpf_prog_active); - preempt_enable(); + bpf_enable_instrumentation(); maybe_wait_bpf_programs(map); if (err) break; |