[PATCH bpf-next v6 13/26] bpf: Allow locking bpf_spin_lock in inner map values

From: Kumar Kartikeya Dwivedi <memxor@gmail.com>
To: bpf@vger.kernel.org
Cc: Alexei Starovoitov <ast@kernel.org>,
	Andrii Nakryiko <andrii@kernel.org>,
	Daniel Borkmann <daniel@iogearbox.net>,
	Martin KaFai Lau <martin.lau@kernel.org>,
	Dave Marchevsky <davemarchevsky@meta.com>,
	Delyan Kratunov <delyank@meta.com>
Subject: [PATCH bpf-next v6 13/26] bpf: Allow locking bpf_spin_lock in inner map values
Date: Sat, 12 Nov 2022 01:02:11 +0530	[thread overview]
Message-ID: <20221111193224.876706-14-memxor@gmail.com> (raw)
In-Reply-To: <20221111193224.876706-1-memxor@gmail.com>

There is no need to restrict users from locking bpf_spin_lock in map
values of inner maps. Each inner map lookup gets a unique reg->id
assigned to the returned PTR_TO_MAP_VALUE which will be preserved after
the NULL check. Distinct lookups into different inner map get unique
IDs, and distinct lookups into same inner map also get unique IDs.

Hence, lift the restriction by removing the check return -ENOTSUPP in
map_in_map.c. Later commits will add comprehensive test cases to ensure
that invalid cases are rejected.

Signed-off-by: Kumar Kartikeya Dwivedi <memxor@gmail.com>
---
 kernel/bpf/map_in_map.c | 5 -----
 1 file changed, 5 deletions(-)

diff --git a/kernel/bpf/map_in_map.c b/kernel/bpf/map_in_map.c
index 8ca0cca39d49..f31893a123a2 100644
--- a/kernel/bpf/map_in_map.c
+++ b/kernel/bpf/map_in_map.c
@@ -29,11 +29,6 @@ struct bpf_map *bpf_map_meta_alloc(int inner_map_ufd)
 		return ERR_PTR(-ENOTSUPP);
 	}
 
-	if (btf_record_has_field(inner_map->record, BPF_SPIN_LOCK)) {
-		fdput(f);
-		return ERR_PTR(-ENOTSUPP);
-	}
-
 	inner_map_meta_size = sizeof(*inner_map_meta);
 	/* In some cases verifier needs to access beyond just base map. */
 	if (inner_map->ops == &array_map_ops)
-- 
2.38.1

