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Commit d66f2b91 authored by Jakub Kicinski's avatar Jakub Kicinski Committed by David S. Miller
Browse files

bpf: don't rely on the verifier lock for metadata_dst allocation 



bpf_skb_set_tunnel_*() functions require allocation of per-cpu
metadata_dst.  The allocation happens upon verification of the
first program using those helpers.  In preparation for removing
the verifier lock, use cmpxchg() to make sure we only allocate
the metadata_dsts once.

Signed-off-by: default avatarJakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: default avatarSimon Horman <simon.horman@netronome.com>
Acked-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent c9c35995

include/net/dst_metadata.h

+1 −0
Original line number Diff line number Diff line
@@ -87,6 +87,7 @@ static inline int skb_metadata_dst_cmp(const struct sk_buff *skb_a, 
void metadata_dst_free(struct metadata_dst *);

struct metadata_dst *metadata_dst_alloc(u8 optslen, enum metadata_type type,

					gfp_t flags);

void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst);

struct metadata_dst __percpu *

metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags);

net/core/dst.c

+16 −0
Original line number Diff line number Diff line
@@ -322,3 +322,19 @@ metadata_dst_alloc_percpu(u8 optslen, enum metadata_type type, gfp_t flags) 
	return md_dst;

}

EXPORT_SYMBOL_GPL(metadata_dst_alloc_percpu);



void metadata_dst_free_percpu(struct metadata_dst __percpu *md_dst)

{

	int cpu;



#ifdef CONFIG_DST_CACHE

	for_each_possible_cpu(cpu) {

		struct metadata_dst *one_md_dst = per_cpu_ptr(md_dst, cpu);



		if (one_md_dst->type == METADATA_IP_TUNNEL)

			dst_cache_destroy(&one_md_dst->u.tun_info.dst_cache);

	}

#endif

	free_percpu(md_dst);

}

EXPORT_SYMBOL_GPL(metadata_dst_free_percpu);

net/core/filter.c

+9 −7
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ 
#include <linux/timer.h>

#include <linux/uaccess.h>

#include <asm/unaligned.h>

#include <asm/cmpxchg.h>

#include <linux/filter.h>

#include <linux/ratelimit.h>

#include <linux/seccomp.h>
@@ -2987,14 +2988,15 @@ static const struct bpf_func_proto * 
bpf_get_skb_set_tunnel_proto(enum bpf_func_id which)

{

	if (!md_dst) {

		/* Race is not possible, since it's called from verifier

		 * that is holding verifier mutex.

		 */

		md_dst = metadata_dst_alloc_percpu(IP_TUNNEL_OPTS_MAX,

		struct metadata_dst __percpu *tmp;



		tmp = metadata_dst_alloc_percpu(IP_TUNNEL_OPTS_MAX,

						METADATA_IP_TUNNEL,

						GFP_KERNEL);

		if (!md_dst)

		if (!tmp)

			return NULL;

		if (cmpxchg(&md_dst, NULL, tmp))

			metadata_dst_free_percpu(tmp);

	}



	switch (which) {