From: Jiri Olsa jolsa@kernel.org
[ Upstream commit 35e3815fa8102fab4dee75f3547472c66581125d ]
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: Alexei Starovoitov ast@kernel.org Signed-off-by: Jiri Olsa jolsa@kernel.org Signed-off-by: Alexei Starovoitov ast@kernel.org Link: https://lore.kernel.org/bpf/20210429114712.43783-1-jolsa@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/bpf/verifier.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index b186d852fe3d..9e600767803b 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -12556,6 +12556,17 @@ int bpf_check_attach_target(struct bpf_verifier_log *log, 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) { struct bpf_prog *prog = env->prog; @@ -12615,6 +12626,9 @@ static int check_attach_btf_id(struct bpf_verifier_env *env) ret = bpf_lsm_verify_prog(&env->log, prog); if (ret < 0) 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);