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authorJiri Olsa <jolsa@kernel.org>2021-04-29 14:47:12 +0300
committerAlexei Starovoitov <ast@kernel.org>2021-05-12 00:00:53 +0300
commit35e3815fa8102fab4dee75f3547472c66581125d (patch)
tree76d9a26444ea4ab3656bc02825453f79a66a71c4 /kernel/bpf
parent08389d888287c3823f80b0216766b71e17f0aba5 (diff)
downloadlinux-35e3815fa8102fab4dee75f3547472c66581125d.tar.xz
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: 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
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/verifier.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 9352a1b7de2d..c58598ef4b5b 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13196,6 +13196,17 @@ 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;
@@ -13255,6 +13266,9 @@ 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);