* [PATCH] bpf: Add deny list of btf ids check for tracing and ext programs
@ 2021-04-28 16:18 Jiri Olsa
2021-04-28 19:41 ` Andrii Nakryiko
0 siblings, 1 reply; 3+ messages in thread
From: Jiri Olsa @ 2021-04-28 16:18 UTC (permalink / raw)
To: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko
Cc: netdev, bpf, Martin KaFai Lau, Song Liu, Yonghong Song,
John Fastabend, KP Singh
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
and ext 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>
---
kernel/bpf/verifier.c | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index 2579f6fbb5c3..4ffd64eaffda 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -13112,6 +13112,17 @@ 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;
@@ -13171,6 +13182,10 @@ 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 ||
+ prog->type == BPF_PROG_TYPE_EXT) &&
+ btf_id_set_contains(&btf_id_deny, btf_id)) {
+ return -EINVAL;
}
key = bpf_trampoline_compute_key(tgt_prog, prog->aux->attach_btf, btf_id);
--
2.30.2
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] bpf: Add deny list of btf ids check for tracing and ext programs
2021-04-28 16:18 [PATCH] bpf: Add deny list of btf ids check for tracing and ext programs Jiri Olsa
@ 2021-04-28 19:41 ` Andrii Nakryiko
2021-04-29 11:24 ` Jiri Olsa
0 siblings, 1 reply; 3+ messages in thread
From: Andrii Nakryiko @ 2021-04-28 19:41 UTC (permalink / raw)
To: Jiri Olsa
Cc: Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Networking,
bpf, Martin KaFai Lau, Song Liu, Yonghong Song, John Fastabend,
KP Singh
On Wed, Apr 28, 2021 at 9:19 AM Jiri Olsa <jolsa@kernel.org> wrote:
>
> 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
> and ext 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>
> ---
> kernel/bpf/verifier.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> index 2579f6fbb5c3..4ffd64eaffda 100644
> --- a/kernel/bpf/verifier.c
> +++ b/kernel/bpf/verifier.c
> @@ -13112,6 +13112,17 @@ 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;
> @@ -13171,6 +13182,10 @@ 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 ||
> + prog->type == BPF_PROG_TYPE_EXT) &&
BPF_PROG_TYP_EXT can only replace other BPF programs/subprograms, it
can't replace kernel functions, so the deny list shouldn't be checked
for them.
> + btf_id_set_contains(&btf_id_deny, btf_id)) {
> + return -EINVAL;
> }
>
> key = bpf_trampoline_compute_key(tgt_prog, prog->aux->attach_btf, btf_id);
> --
> 2.30.2
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] bpf: Add deny list of btf ids check for tracing and ext programs
2021-04-28 19:41 ` Andrii Nakryiko
@ 2021-04-29 11:24 ` Jiri Olsa
0 siblings, 0 replies; 3+ messages in thread
From: Jiri Olsa @ 2021-04-29 11:24 UTC (permalink / raw)
To: Andrii Nakryiko
Cc: Jiri Olsa, Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko,
Networking, bpf, Martin KaFai Lau, Song Liu, Yonghong Song,
John Fastabend, KP Singh
On Wed, Apr 28, 2021 at 12:41:34PM -0700, Andrii Nakryiko wrote:
> On Wed, Apr 28, 2021 at 9:19 AM Jiri Olsa <jolsa@kernel.org> wrote:
> >
> > 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
> > and ext 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>
> > ---
> > kernel/bpf/verifier.c | 15 +++++++++++++++
> > 1 file changed, 15 insertions(+)
> >
> > diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
> > index 2579f6fbb5c3..4ffd64eaffda 100644
> > --- a/kernel/bpf/verifier.c
> > +++ b/kernel/bpf/verifier.c
> > @@ -13112,6 +13112,17 @@ 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;
> > @@ -13171,6 +13182,10 @@ 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 ||
> > + prog->type == BPF_PROG_TYPE_EXT) &&
>
> BPF_PROG_TYP_EXT can only replace other BPF programs/subprograms, it
> can't replace kernel functions, so the deny list shouldn't be checked
> for them.
right, will send new version
jirka
>
> > + btf_id_set_contains(&btf_id_deny, btf_id)) {
> > + return -EINVAL;
> > }
> >
> > key = bpf_trampoline_compute_key(tgt_prog, prog->aux->attach_btf, btf_id);
> > --
> > 2.30.2
> >
>
^ permalink raw reply [flat|nested] 3+ messages in thread
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2021-04-28 16:18 [PATCH] bpf: Add deny list of btf ids check for tracing and ext programs Jiri Olsa
2021-04-28 19:41 ` Andrii Nakryiko
2021-04-29 11:24 ` Jiri Olsa
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