Commit 3960f4fd authored Jul 13, 2018 by Roman Gushchin Committed by Daniel Borkmann Jul 18, 2018

bpf: fix rcu annotations in compute_effective_progs()



The progs local variable in compute_effective_progs() is marked
as __rcu, which is not correct. This is a local pointer, which
is initialized by bpf_prog_array_alloc(), which also now
returns a generic non-rcu pointer.

The real rcu-protected pointer is *array (array is a pointer
to an RCU-protected pointer), so the assignment should be performed
using rcu_assign_pointer().

Fixes: 324bda9e ("bpf: multi program support for cgroup+bpf")
Signed-off-by: Roman Gushchin <guro@fb.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

parent d29ab6e1

kernel/bpf/cgroup.c

+3 −4

Original line number	Diff line number	Diff line
		@@ -95,7 +95,7 @@ static int compute_effective_progs(struct cgroup *cgrp,
		enum bpf_attach_type type,
		struct bpf_prog_array __rcu **array)
		{
		struct bpf_prog_array __rcu *progs;
		struct bpf_prog_array *progs;
		struct bpf_prog_list *pl;
		struct cgroup *p = cgrp;
		int cnt = 0;
		@@ -120,13 +120,12 @@ static int compute_effective_progs(struct cgroup *cgrp,
		&p->bpf.progs[type], node) {
		if (!pl->prog)
		continue;
		rcu_dereference_protected(progs, 1)->
		progs[cnt++] = pl->prog;
		progs->progs[cnt++] = pl->prog;
		}
		p = cgroup_parent(p);
		} while (p);

		*array = progs;
		rcu_assign_pointer(*array, progs);
		return 0;
		}

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