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bpf: Use bpf_prog_run_pin_on_cpu() at simple call sites.

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All of these cases are strictly of the form:

	preempt_disable();
	BPF_PROG_RUN(...);
	preempt_enable();

Replace this with bpf_prog_run_pin_on_cpu() which wraps BPF_PROG_RUN()
with:

	migrate_disable();
	BPF_PROG_RUN(...);
	migrate_enable();

On non RT enabled kernels this maps to preempt_disable/enable() and on RT
enabled kernels this solely prevents migration, which is sufficient as
there is no requirement to prevent reentrancy to any BPF program from a
preempting task. The only requirement is that the program stays on the same
CPU.

Therefore, this is a trivially correct transformation.

The seccomp loop does not need protection over the loop. It only needs
protection per BPF filter program

[ tglx: Converted to bpf_prog_run_pin_on_cpu() ]

Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200224145643.691493094@linutronix.de
This commit is contained in:
David Miller 2020-02-24 15:01:43 +01:00 • committed by Alexei Starovoitov
parent 37e1d92022
commit 3d9f773cf2
5 changed files with 6 additions and 18 deletions
Download patch file Download diff file Expand all files Collapse all files

4
include/linux/filter.h
View file

@ -717,9 +717,7 @@ static inline u32 bpf_prog_run_clear_cb(const struct bpf_prog *prog,
if (unlikely(prog->cb_access)) if (unlikely(prog->cb_access))
memset(cb_data, 0, BPF_SKB_CB_LEN); memset(cb_data, 0, BPF_SKB_CB_LEN);
preempt_disable(); res = bpf_prog_run_pin_on_cpu(prog, skb);
res = BPF_PROG_RUN(prog, skb);
preempt_enable();
return res; return res;
} }

4
kernel/seccomp.c
View file

@ -268,16 +268,14 @@ static u32 seccomp_run_filters(const struct seccomp_data *sd,
* All filters in the list are evaluated and the lowest BPF return * All filters in the list are evaluated and the lowest BPF return
* value always takes priority (ignoring the DATA). * value always takes priority (ignoring the DATA).
*/ */
preempt_disable();
for (; f; f = f->prev) { for (; f; f = f->prev) {
u32 cur_ret = BPF_PROG_RUN(f->prog, sd); u32 cur_ret = bpf_prog_run_pin_on_cpu(f->prog, sd);
if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) { if (ACTION_ONLY(cur_ret) < ACTION_ONLY(ret)) {
ret = cur_ret; ret = cur_ret;
*match = f; *match = f;
} }
} }
preempt_enable();
return ret; return ret;
} }
#endif /* CONFIG_SECCOMP_FILTER */ #endif /* CONFIG_SECCOMP_FILTER */

4
net/core/flow_dissector.c
View file

@ -920,9 +920,7 @@ bool bpf_flow_dissect(struct bpf_prog *prog, struct bpf_flow_dissector *ctx,
(int)FLOW_DISSECTOR_F_STOP_AT_ENCAP); (int)FLOW_DISSECTOR_F_STOP_AT_ENCAP);
flow_keys->flags = flags; flow_keys->flags = flags;
preempt_disable(); result = bpf_prog_run_pin_on_cpu(prog, ctx);
result = BPF_PROG_RUN(prog, ctx);
preempt_enable();
flow_keys->nhoff = clamp_t(u16, flow_keys->nhoff, nhoff, hlen); flow_keys->nhoff = clamp_t(u16, flow_keys->nhoff, nhoff, hlen);
flow_keys->thoff = clamp_t(u16, flow_keys->thoff, flow_keys->thoff = clamp_t(u16, flow_keys->thoff,

8
net/core/skmsg.c
View file

@ -628,7 +628,6 @@ int sk_psock_msg_verdict(struct sock *sk, struct sk_psock *psock,
struct bpf_prog *prog; struct bpf_prog *prog;
int ret; int ret;
preempt_disable();
rcu_read_lock(); rcu_read_lock();
prog = READ_ONCE(psock->progs.msg_parser); prog = READ_ONCE(psock->progs.msg_parser);
if (unlikely(!prog)) { if (unlikely(!prog)) {
@ -638,7 +637,7 @@ int sk_psock_msg_verdict(struct sock *sk, struct sk_psock *psock,
sk_msg_compute_data_pointers(msg); sk_msg_compute_data_pointers(msg);
msg->sk = sk; msg->sk = sk;
ret = BPF_PROG_RUN(prog, msg); ret = bpf_prog_run_pin_on_cpu(prog, msg);
ret = sk_psock_map_verd(ret, msg->sk_redir); ret = sk_psock_map_verd(ret, msg->sk_redir);
psock->apply_bytes = msg->apply_bytes; psock->apply_bytes = msg->apply_bytes;
if (ret == __SK_REDIRECT) { if (ret == __SK_REDIRECT) {
@ -653,7 +652,6 @@ int sk_psock_msg_verdict(struct sock *sk, struct sk_psock *psock,
} }
out: out:
rcu_read_unlock(); rcu_read_unlock();
preempt_enable();
return ret; return ret;
} }
EXPORT_SYMBOL_GPL(sk_psock_msg_verdict); EXPORT_SYMBOL_GPL(sk_psock_msg_verdict);
@ -665,9 +663,7 @@ static int sk_psock_bpf_run(struct sk_psock *psock, struct bpf_prog *prog,
skb->sk = psock->sk; skb->sk = psock->sk;
bpf_compute_data_end_sk_skb(skb); bpf_compute_data_end_sk_skb(skb);
preempt_disable(); ret = bpf_prog_run_pin_on_cpu(prog, skb);
ret = BPF_PROG_RUN(prog, skb);
preempt_enable();
/* strparser clones the skb before handing it to a upper layer, /* strparser clones the skb before handing it to a upper layer,
* meaning skb_orphan has been called. We NULL sk on the way out * meaning skb_orphan has been called. We NULL sk on the way out
* to ensure we don't trigger a BUG_ON() in skb/sk operations * to ensure we don't trigger a BUG_ON() in skb/sk operations

4
net/kcm/kcmsock.c
View file

@ -380,9 +380,7 @@ static int kcm_parse_func_strparser(struct strparser *strp, struct sk_buff *skb)
struct bpf_prog *prog = psock->bpf_prog; struct bpf_prog *prog = psock->bpf_prog;
int res; int res;
preempt_disable(); res = bpf_prog_run_pin_on_cpu(prog, skb);
res = BPF_PROG_RUN(prog, skb);
preempt_enable();
return res; return res;
} }