Commit 35e3815f authored by Jiri Olsa's avatar Jiri Olsa Committed by Alexei Starovoitov

bpf: Add deny list of btf ids check for tracing programs

The recursion check in __bpf_prog_enter and __bpf_prog_exit
leaves some (not inlined) functions unprotected:

In __bpf_prog_enter:
  - migrate_disable is called before prog->active is checked

In __bpf_prog_exit:
  - migrate_enable,rcu_read_unlock_strict are called after
    prog->active is decreased

When attaching trampoline to them we get panic like:

  traps: PANIC: double fault, error_code: 0x0
  double fault: 0000 [#1] SMP PTI
  RIP: 0010:__bpf_prog_enter+0x4/0x50
  ...
  Call Trace:
   <IRQ>
   bpf_trampoline_6442466513_0+0x18/0x1000
   migrate_disable+0x5/0x50
   __bpf_prog_enter+0x9/0x50
   bpf_trampoline_6442466513_0+0x18/0x1000
   migrate_disable+0x5/0x50
   __bpf_prog_enter+0x9/0x50
   bpf_trampoline_6442466513_0+0x18/0x1000
   migrate_disable+0x5/0x50
   __bpf_prog_enter+0x9/0x50
   bpf_trampoline_6442466513_0+0x18/0x1000
   migrate_disable+0x5/0x50
   ...

Fixing this by adding deny list of btf ids for tracing
programs and checking btf id during program verification.
Adding above functions to this list.
Suggested-by: default avatarAlexei Starovoitov <ast@kernel.org>
Signed-off-by: default avatarJiri Olsa <jolsa@kernel.org>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210429114712.43783-1-jolsa@kernel.org
parent 08389d88
...@@ -13196,6 +13196,17 @@ int bpf_check_attach_target(struct bpf_verifier_log *log, ...@@ -13196,6 +13196,17 @@ int bpf_check_attach_target(struct bpf_verifier_log *log,
return 0; return 0;
} }
BTF_SET_START(btf_id_deny)
BTF_ID_UNUSED
#ifdef CONFIG_SMP
BTF_ID(func, migrate_disable)
BTF_ID(func, migrate_enable)
#endif
#if !defined CONFIG_PREEMPT_RCU && !defined CONFIG_TINY_RCU
BTF_ID(func, rcu_read_unlock_strict)
#endif
BTF_SET_END(btf_id_deny)
static int check_attach_btf_id(struct bpf_verifier_env *env) static int check_attach_btf_id(struct bpf_verifier_env *env)
{ {
struct bpf_prog *prog = env->prog; struct bpf_prog *prog = env->prog;
...@@ -13255,6 +13266,9 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) ...@@ -13255,6 +13266,9 @@ static int check_attach_btf_id(struct bpf_verifier_env *env)
ret = bpf_lsm_verify_prog(&env->log, prog); ret = bpf_lsm_verify_prog(&env->log, prog);
if (ret < 0) if (ret < 0)
return ret; return ret;
} else if (prog->type == BPF_PROG_TYPE_TRACING &&
btf_id_set_contains(&btf_id_deny, btf_id)) {
return -EINVAL;
} }
key = bpf_trampoline_compute_key(tgt_prog, prog->aux->attach_btf, btf_id); key = bpf_trampoline_compute_key(tgt_prog, prog->aux->attach_btf, btf_id);
......
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