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bpf: Add cookie object to bpf maps

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Add a cookie to BPF maps to uniquely identify BPF maps for the timespan
when the node is up. This is different to comparing a pointer or BPF map
id which could get rolled over and reused.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/r/20250730234733.530041-1-daniel@iogearbox.net
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Daniel Borkmann
2025-07-31 01:47:30 +02:00
committed by Alexei Starovoitov
parent d6084bb815
commit 12df58ad29
2 changed files with 7 additions and 0 deletions
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1
include/linux/bpf.h
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@@ -310,6 +310,7 @@ struct bpf_map {
bool free_after_rcu_gp;
atomic64_t sleepable_refcnt;
s64 __percpu *elem_count;
u64 cookie; /* write-once */
};
static inline const char *btf_field_type_name(enum btf_field_type type)

6
kernel/bpf/syscall.c
View File

@@ -37,6 +37,7 @@
#include <linux/trace_events.h>
#include <linux/tracepoint.h>
#include <linux/overflow.h>
#include <linux/cookie.h>
#include <net/netfilter/nf_bpf_link.h>
#include <net/netkit.h>
@@ -53,6 +54,7 @@
#define BPF_OBJ_FLAG_MASK (BPF_F_RDONLY | BPF_F_WRONLY)
DEFINE_PER_CPU(int, bpf_prog_active);
DEFINE_COOKIE(bpf_map_cookie);
static DEFINE_IDR(prog_idr);
static DEFINE_SPINLOCK(prog_idr_lock);
static DEFINE_IDR(map_idr);
@@ -1487,6 +1489,10 @@ static int map_create(union bpf_attr *attr, bool kernel)
if (err < 0)
goto free_map;
preempt_disable();
map->cookie = gen_cookie_next(&bpf_map_cookie);
preempt_enable();
atomic64_set(&map->refcnt, 1);
atomic64_set(&map->usercnt, 1);
mutex_init(&map->freeze_mutex);