67 lines
2.5 KiB
Diff
67 lines
2.5 KiB
Diff
From 9b6f4eb1570c219474f6029caea71584d7a2188a Mon Sep 17 00:00:00 2001
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From: Anquan Wu <leiqi96@hotmail.com>
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Date: Tue, 12 Jul 2022 11:15:40 +0800
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Subject: [PATCH] libbpf: Fix the name of a reused map
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MIME-Version: 1.0
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Content-Type: text/plain; charset=UTF-8
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Content-Transfer-Encoding: 8bit
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BPF map name is limited to BPF_OBJ_NAME_LEN.
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A map name is defined as being longer than BPF_OBJ_NAME_LEN,
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it will be truncated to BPF_OBJ_NAME_LEN when a userspace program
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calls libbpf to create the map. A pinned map also generates a path
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in the /sys. If the previous program wanted to reuse the map，
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it can not get bpf_map by name, because the name of the map is only
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partially the same as the name which get from pinned path.
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The syscall information below show that map name "process_pinned_map"
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is truncated to "process_pinned_".
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bpf(BPF_OBJ_GET, {pathname="/sys/fs/bpf/process_pinned_map",
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bpf_fd=0, file_flags=0}, 144) = -1 ENOENT (No such file or directory)
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bpf(BPF_MAP_CREATE, {map_type=BPF_MAP_TYPE_HASH, key_size=4,
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value_size=4,max_entries=1024, map_flags=0, inner_map_fd=0,
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map_name="process_pinned_",map_ifindex=0, btf_fd=3, btf_key_type_id=6,
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btf_value_type_id=10,btf_vmlinux_value_type_id=0}, 72) = 4
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This patch check that if the name of pinned map are the same as the
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actual name for the first (BPF_OBJ_NAME_LEN - 1),
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bpf map still uses the name which is included in bpf object.
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Fixes: 26736eb9a483 ("tools: libbpf: allow map reuse")
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Signed-off-by: Anquan Wu <leiqi96@hotmail.com>
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Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
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Link: https://lore.kernel.org/bpf/OSZP286MB1725CEA1C95C5CB8E7CCC53FB8869@OSZP286MB1725.JPNP286.PROD.OUTLOOK.COM
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---
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src/libbpf.c | 9 +++++++--
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1 file changed, 7 insertions(+), 2 deletions(-)
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diff --git a/src/libbpf.c b/src/libbpf.c
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index 72548798..68da1aca 100644
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--- a/src/libbpf.c
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+++ b/src/libbpf.c
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@@ -4327,7 +4327,7 @@ int bpf_map__set_autocreate(struct bpf_map *map, bool autocreate)
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int bpf_map__reuse_fd(struct bpf_map *map, int fd)
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{
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struct bpf_map_info info = {};
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- __u32 len = sizeof(info);
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+ __u32 len = sizeof(info), name_len;
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int new_fd, err;
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char *new_name;
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@@ -4337,7 +4337,12 @@ int bpf_map__reuse_fd(struct bpf_map *map, int fd)
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if (err)
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return libbpf_err(err);
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- new_name = strdup(info.name);
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+ name_len = strlen(info.name);
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+ if (name_len == BPF_OBJ_NAME_LEN - 1 && strncmp(map->name, info.name, name_len) == 0)
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+ new_name = strdup(map->name);
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+ else
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+ new_name = strdup(info.name);
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+
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if (!new_name)
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return libbpf_err(-errno);
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