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Commit 6cab5e90 authored by Alexei Starovoitov's avatar Alexei Starovoitov Committed by Daniel Borkmann
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bpf: run bpf programs with preemption disabled 



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: default avatarJann Horn <jannh@google.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarSong Liu <songliubraving@fb.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
parent 1bb54c40

include/linux/filter.h

+18 −3
Original line number Diff line number Diff line
@@ -591,7 +591,7 @@ 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,

static inline u32 __bpf_prog_run_save_cb(const struct bpf_prog *prog,

					 struct sk_buff *skb)

{

	u8 *cb_data = bpf_skb_cb(skb);
@@ -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,

kernel/bpf/cgroup.c

+1 −1
Original line number Diff line number Diff line
@@ -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;