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bpftool: Fix vmlinux BTF leak in cgroup commands

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bpftool cgroup show and tree call libbpf_find_kernel_btf() to
resolve attach_btf names, but never release the returned BTF object.

For cgroup tree, do_show_tree_fn() is called once for each cgroup
visited by nftw(). When more than one cgroup has attached programs,
each callback overwrites btf_vmlinux with a new object and loses the
previous allocation.

Load vmlinux BTF only once during a tree walk and release it when
cgroup show or tree completes. Reset btf_vmlinux_id at the same time
so batch mode starts with clean state.

Fixes: 596f5fb2ea ("bpftool: implement cgroup tree for BPF_LSM_CGROUP")
Signed-off-by: Yichong Chen <chenyichong@uniontech.com>
Reviewed-by: Quentin Monnet <qmo@kernel.org>
Link: https://lore.kernel.org/r/24357C69B4405079+20260617090117.280222-1-chenyichong@uniontech.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Yichong Chen
2026-06-17 17:01:17 +08:00
committed by Alexei Starovoitov
parent d5dc200c3a
commit bda6a7308e
1 changed files with 13 additions and 1 deletions
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14
tools/bpf/bpftool/cgroup.c
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@@ -78,6 +78,13 @@ static unsigned int query_flags;
static struct btf *btf_vmlinux;
static __u32 btf_vmlinux_id;
static void free_btf_vmlinux(void)
{
btf__free(btf_vmlinux);
btf_vmlinux = NULL;
btf_vmlinux_id = 0;
}
static enum bpf_attach_type parse_attach_type(const char *str)
{
const char *attach_type_str;
@@ -388,6 +395,8 @@ static int do_show(int argc, char **argv)
if (json_output)
jsonw_end_array(json_wtr);
free_btf_vmlinux();
exit_cgroup:
close(cgroup_fd);
exit:
@@ -437,7 +446,9 @@ static int do_show_tree_fn(const char *fpath, const struct stat *sb,
printf("%s\n", fpath);
}
btf_vmlinux = libbpf_find_kernel_btf();
if (!btf_vmlinux)
btf_vmlinux = libbpf_find_kernel_btf();
for (i = 0; i < ARRAY_SIZE(cgroup_attach_types); i++)
show_bpf_progs(cgroup_fd, cgroup_attach_types[i], ftw->level);
@@ -540,6 +551,7 @@ static int do_show_tree(int argc, char **argv)
if (json_output)
jsonw_end_array(json_wtr);
free_btf_vmlinux();
free(cgroup_alloced);
return ret;