From 12df58ad294253ac1d8df0c9bb9cf726397a671d Mon Sep 17 00:00:00 2001 From: Daniel Borkmann Date: Thu, 31 Jul 2025 01:47:30 +0200 Subject: [PATCH] bpf: Add cookie object to bpf maps 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 Link: https://lore.kernel.org/r/20250730234733.530041-1-daniel@iogearbox.net Signed-off-by: Alexei Starovoitov --- 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 f9cd2164ed238..308530c8326bf 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 e63039817af38..7a814e98d5f5c 100644 --- a/kernel/bpf/syscall.c +++ b/kernel/bpf/syscall.c @@ -37,6 +37,7 @@ #include #include #include +#include #include #include @@ -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); -- 2.47.2