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Subject[PATCH 4.20 051/352] bpf: libbpf: retry map creation without the name
Date
4.20-stable review patch.  If anyone has any objections, please let me know.

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

[ Upstream commit 23499442c319412aa8e54e7a939e2eb531bdd77d ]

Since commit 88cda1c9da02 ("bpf: libbpf: Provide basic API support
to specify BPF obj name"), libbpf unconditionally sets bpf_attr->name
for maps. Pre v4.14 kernels don't know about map names and return an
error about unexpected non-zero data. Retry sys_bpf without a map
name to cover older kernels.

v2 changes:
* check for errno == EINVAL as suggested by Daniel Borkmann

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
tools/lib/bpf/bpf.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index 03f9bcc4ef50..961e1b9fc592 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -69,6 +69,7 @@ int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
{
__u32 name_len = create_attr->name ? strlen(create_attr->name) : 0;
union bpf_attr attr;
+ int ret;

memset(&attr, '\0', sizeof(attr));

@@ -86,7 +87,15 @@ int bpf_create_map_xattr(const struct bpf_create_map_attr *create_attr)
attr.map_ifindex = create_attr->map_ifindex;
attr.inner_map_fd = create_attr->inner_map_fd;

- return sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+ ret = sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+ if (ret < 0 && errno == EINVAL && create_attr->name) {
+ /* Retry the same syscall, but without the name.
+ * Pre v4.14 kernels don't support map names.
+ */
+ memset(attr.map_name, 0, sizeof(attr.map_name));
+ return sys_bpf(BPF_MAP_CREATE, &attr, sizeof(attr));
+ }
+ return ret;
}

int bpf_create_map_node(enum bpf_map_type map_type, const char *name,
--
2.19.1


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