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@xxxxxxxxxxxxx>
---
include/linux/bpf.h | 1 +
kernel/bpf/syscall.c | 6 ++++++
2 files changed, 7 insertions(+)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index f9cd2164ed23..308530c8326b 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -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)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index e63039817af3..7a814e98d5f5 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -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);
--
2.43.0
