* [PATCH bpf] bpf: run bpf programs with preemption disabled
@ 2019-01-29 2:43 Alexei Starovoitov
2019-01-29 7:01 ` Song Liu
2019-01-31 22:24 ` Daniel Borkmann
0 siblings, 2 replies; 3+ messages in thread
From: Alexei Starovoitov @ 2019-01-29 2:43 UTC (permalink / raw)
To: davem
Cc: daniel, peterz, jannh, paulmck, will.deacon, mingo, netdev,
kernel-team
Disabled preemption is necessary for proper access to per-cpu maps
from BPF programs.
But the sender side of socket filters didn't have preemption disabled:
unix_dgram_sendmsg->sk_filter->sk_filter_trim_cap->bpf_prog_run_save_cb->BPF_PROG_RUN
and a combination of af_packet with tun device didn't disable either:
tpacket_snd->packet_direct_xmit->packet_pick_tx_queue->ndo_select_queue->
tun_select_queue->tun_ebpf_select_queue->bpf_prog_run_clear_cb->BPF_PROG_RUN
Disable preemption before executing BPF programs (both classic and extended).
Reported-by: Jann Horn <jannh@google.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
---
include/linux/filter.h | 21 ++++++++++++++++++---
kernel/bpf/cgroup.c | 2 +-
2 files changed, 19 insertions(+), 4 deletions(-)
diff --git a/include/linux/filter.h b/include/linux/filter.h
index ad106d845b22..e532fcc6e4b5 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -591,8 +591,8 @@ static inline u8 *bpf_skb_cb(struct sk_buff *skb)
return qdisc_skb_cb(skb)->data;
}
-static inline u32 bpf_prog_run_save_cb(const struct bpf_prog *prog,
- struct sk_buff *skb)
+static inline u32 __bpf_prog_run_save_cb(const struct bpf_prog *prog,
+ struct sk_buff *skb)
{
u8 *cb_data = bpf_skb_cb(skb);
u8 cb_saved[BPF_SKB_CB_LEN];
@@ -611,15 +611,30 @@ static inline u32 bpf_prog_run_save_cb(const struct bpf_prog *prog,
return res;
}
+static inline u32 bpf_prog_run_save_cb(const struct bpf_prog *prog,
+ struct sk_buff *skb)
+{
+ u32 res;
+
+ preempt_disable();
+ res = __bpf_prog_run_save_cb(prog, skb);
+ preempt_enable();
+ return res;
+}
+
static inline u32 bpf_prog_run_clear_cb(const struct bpf_prog *prog,
struct sk_buff *skb)
{
u8 *cb_data = bpf_skb_cb(skb);
+ u32 res;
if (unlikely(prog->cb_access))
memset(cb_data, 0, BPF_SKB_CB_LEN);
- return BPF_PROG_RUN(prog, skb);
+ preempt_disable();
+ res = BPF_PROG_RUN(prog, skb);
+ preempt_enable();
+ return res;
}
static __always_inline u32 bpf_prog_run_xdp(const struct bpf_prog *prog,
diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index ab612fe9862f..d17d05570a3f 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -572,7 +572,7 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
bpf_compute_and_save_data_end(skb, &saved_data_end);
ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], skb,
- bpf_prog_run_save_cb);
+ __bpf_prog_run_save_cb);
bpf_restore_data_end(skb, saved_data_end);
__skb_pull(skb, offset);
skb->sk = save_sk;
--
2.20.0
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH bpf] bpf: run bpf programs with preemption disabled
2019-01-29 2:43 [PATCH bpf] bpf: run bpf programs with preemption disabled Alexei Starovoitov
@ 2019-01-29 7:01 ` Song Liu
2019-01-31 22:24 ` Daniel Borkmann
1 sibling, 0 replies; 3+ messages in thread
From: Song Liu @ 2019-01-29 7:01 UTC (permalink / raw)
To: Alexei Starovoitov
Cc: David Miller, daniel@iogearbox.net, peterz@infradead.org,
jannh@google.com, paulmck@linux.ibm.com, will.deacon@arm.com,
mingo@redhat.com, netdev@vger.kernel.org, Kernel Team
> On Jan 28, 2019, at 6:43 PM, Alexei Starovoitov <ast@kernel.org> wrote:
>
> Disabled preemption is necessary for proper access to per-cpu maps
> from BPF programs.
>
> But the sender side of socket filters didn't have preemption disabled:
> unix_dgram_sendmsg->sk_filter->sk_filter_trim_cap->bpf_prog_run_save_cb->BPF_PROG_RUN
>
> and a combination of af_packet with tun device didn't disable either:
> tpacket_snd->packet_direct_xmit->packet_pick_tx_queue->ndo_select_queue->
> tun_select_queue->tun_ebpf_select_queue->bpf_prog_run_clear_cb->BPF_PROG_RUN
>
> Disable preemption before executing BPF programs (both classic and extended).
>
> Reported-by: Jann Horn <jannh@google.com>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
> ---
> include/linux/filter.h | 21 ++++++++++++++++++---
> kernel/bpf/cgroup.c | 2 +-
> 2 files changed, 19 insertions(+), 4 deletions(-)
>
> diff --git a/include/linux/filter.h b/include/linux/filter.h
> index ad106d845b22..e532fcc6e4b5 100644
> --- a/include/linux/filter.h
> +++ b/include/linux/filter.h
> @@ -591,8 +591,8 @@ static inline u8 *bpf_skb_cb(struct sk_buff *skb)
> return qdisc_skb_cb(skb)->data;
> }
>
> -static inline u32 bpf_prog_run_save_cb(const struct bpf_prog *prog,
> - struct sk_buff *skb)
> +static inline u32 __bpf_prog_run_save_cb(const struct bpf_prog *prog,
> + struct sk_buff *skb)
> {
> u8 *cb_data = bpf_skb_cb(skb);
> u8 cb_saved[BPF_SKB_CB_LEN];
> @@ -611,15 +611,30 @@ static inline u32 bpf_prog_run_save_cb(const struct bpf_prog *prog,
> return res;
> }
>
> +static inline u32 bpf_prog_run_save_cb(const struct bpf_prog *prog,
> + struct sk_buff *skb)
> +{
> + u32 res;
> +
> + preempt_disable();
> + res = __bpf_prog_run_save_cb(prog, skb);
> + preempt_enable();
> + return res;
> +}
> +
> static inline u32 bpf_prog_run_clear_cb(const struct bpf_prog *prog,
> struct sk_buff *skb)
> {
> u8 *cb_data = bpf_skb_cb(skb);
> + u32 res;
>
> if (unlikely(prog->cb_access))
> memset(cb_data, 0, BPF_SKB_CB_LEN);
>
> - return BPF_PROG_RUN(prog, skb);
> + preempt_disable();
> + res = BPF_PROG_RUN(prog, skb);
> + preempt_enable();
> + return res;
> }
>
> static __always_inline u32 bpf_prog_run_xdp(const struct bpf_prog *prog,
> diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
> index ab612fe9862f..d17d05570a3f 100644
> --- a/kernel/bpf/cgroup.c
> +++ b/kernel/bpf/cgroup.c
> @@ -572,7 +572,7 @@ int __cgroup_bpf_run_filter_skb(struct sock *sk,
> bpf_compute_and_save_data_end(skb, &saved_data_end);
>
> ret = BPF_PROG_RUN_ARRAY(cgrp->bpf.effective[type], skb,
> - bpf_prog_run_save_cb);
> + __bpf_prog_run_save_cb);
> bpf_restore_data_end(skb, saved_data_end);
> __skb_pull(skb, offset);
> skb->sk = save_sk;
> --
> 2.20.0
>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH bpf] bpf: run bpf programs with preemption disabled
2019-01-29 2:43 [PATCH bpf] bpf: run bpf programs with preemption disabled Alexei Starovoitov
2019-01-29 7:01 ` Song Liu
@ 2019-01-31 22:24 ` Daniel Borkmann
1 sibling, 0 replies; 3+ messages in thread
From: Daniel Borkmann @ 2019-01-31 22:24 UTC (permalink / raw)
To: Alexei Starovoitov, davem
Cc: peterz, jannh, paulmck, will.deacon, mingo, netdev, kernel-team
On 01/29/2019 03:43 AM, Alexei Starovoitov wrote:
> Disabled preemption is necessary for proper access to per-cpu maps
> from BPF programs.
>
> But the sender side of socket filters didn't have preemption disabled:
> unix_dgram_sendmsg->sk_filter->sk_filter_trim_cap->bpf_prog_run_save_cb->BPF_PROG_RUN
>
> and a combination of af_packet with tun device didn't disable either:
> tpacket_snd->packet_direct_xmit->packet_pick_tx_queue->ndo_select_queue->
> tun_select_queue->tun_ebpf_select_queue->bpf_prog_run_clear_cb->BPF_PROG_RUN
>
> Disable preemption before executing BPF programs (both classic and extended).
>
> Reported-by: Jann Horn <jannh@google.com>
> Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Applied, thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
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2019-01-29 7:01 ` Song Liu
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