[PATCH 5.15 01/64] bpf: Add cookie object to bpf maps

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

5.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Daniel Borkmann <daniel@iogearbox.net>

[ Upstream commit 12df58ad294253ac1d8df0c9bb9cf726397a671d ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 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 4236de05a8e70..dd6a62134e7d1 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -200,6 +200,7 @@ struct bpf_map {
 	struct mutex freeze_mutex;
 	atomic64_t writecnt;
 	bool free_after_mult_rcu_gp;
+	u64 cookie; /* write-once */
 };
 
 static inline bool map_value_has_spin_lock(const struct bpf_map *map)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 6f309248f13fc..6d4d08f57ad38 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -31,6 +31,7 @@
 #include <linux/bpf-netns.h>
 #include <linux/rcupdate_trace.h>
 #include <linux/memcontrol.h>
+#include <linux/cookie.h>
 
 #define IS_FD_ARRAY(map) ((map)->map_type == BPF_MAP_TYPE_PERF_EVENT_ARRAY || \
 			  (map)->map_type == BPF_MAP_TYPE_CGROUP_ARRAY || \
@@ -43,6 +44,7 @@
 #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);
@@ -886,6 +888,10 @@ static int map_create(union bpf_attr *attr)
 	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);
-- 
2.50.1