linux-kernel - [PATCH 5.15 046/244] bpf: Acquire map uref in .init_seq_private for sock local storage map iterator

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Date:   Tue, 23 Aug 2022 10:23:25 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Hou Tao <houtao1@...wei.com>,
        Yonghong Song <yhs@...com>, Martin KaFai Lau <kafai@...com>,
        Alexei Starovoitov <ast@...nel.org>
Subject: [PATCH 5.15 046/244] bpf: Acquire map uref in .init_seq_private for sock local storage map iterator

From: Hou Tao <houtao1@...wei.com>

commit 3c5f6e698b5c538bbb23cd453b22e1e4922cffd8 upstream.

bpf_iter_attach_map() acquires a map uref, and the uref may be released
before or in the middle of iterating map elements. For example, the uref
could be released in bpf_iter_detach_map() as part of
bpf_link_release(), or could be released in bpf_map_put_with_uref() as
part of bpf_map_release().

So acquiring an extra map uref in bpf_iter_init_sk_storage_map() and
releasing it in bpf_iter_fini_sk_storage_map().

Fixes: 5ce6e77c7edf ("bpf: Implement bpf iterator for sock local storage map")
Signed-off-by: Hou Tao <houtao1@...wei.com>
Acked-by: Yonghong Song <yhs@...com>
Acked-by: Martin KaFai Lau <kafai@...com>
Link: https://lore.kernel.org/r/20220810080538.1845898-4-houtao@huaweicloud.com
Signed-off-by: Alexei Starovoitov <ast@...nel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/core/bpf_sk_storage.c |   10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

--- a/net/core/bpf_sk_storage.c
+++ b/net/core/bpf_sk_storage.c
@@ -865,10 +865,18 @@ static int bpf_iter_init_sk_storage_map(
 {
 	struct bpf_iter_seq_sk_storage_map_info *seq_info = priv_data;
 
+	bpf_map_inc_with_uref(aux->map);
 	seq_info->map = aux->map;
 	return 0;
 }
 
+static void bpf_iter_fini_sk_storage_map(void *priv_data)
+{
+	struct bpf_iter_seq_sk_storage_map_info *seq_info = priv_data;
+
+	bpf_map_put_with_uref(seq_info->map);
+}
+
 static int bpf_iter_attach_map(struct bpf_prog *prog,
 			       union bpf_iter_link_info *linfo,
 			       struct bpf_iter_aux_info *aux)
@@ -914,7 +922,7 @@ static const struct seq_operations bpf_s
 static const struct bpf_iter_seq_info iter_seq_info = {
 	.seq_ops		= &bpf_sk_storage_map_seq_ops,
 	.init_seq_private	= bpf_iter_init_sk_storage_map,
-	.fini_seq_private	= NULL,
+	.fini_seq_private	= bpf_iter_fini_sk_storage_map,
 	.seq_priv_size		= sizeof(struct bpf_iter_seq_sk_storage_map_info),
 };