Commit cb4a21ea authored by David Vernet's avatar David Vernet Committed by Alexei Starovoitov
Browse files

bpf: Build-time assert that cpumask offset is zero 



The first element of a struct bpf_cpumask is a cpumask_t. This is done
to allow struct bpf_cpumask to be cast to a struct cpumask. If this
element were ever moved to another field, any BPF program passing a
struct bpf_cpumask * to a kfunc expecting a const struct cpumask * would
immediately fail to load. Add a build-time assertion so this is
assumption is captured and verified.

Signed-off-by: default avatarDavid Vernet <void@manifault.com>
Link: https://lore.kernel.org/r/20230128141537.100777-1-void@manifault.com


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 70eb3911

kernel/bpf/cpumask.c

+3 −0
Original line number Diff line number Diff line
@@ -52,6 +52,9 @@ struct bpf_cpumask *bpf_cpumask_create(void) 
{

	struct bpf_cpumask *cpumask;



	/* cpumask must be the first element so struct bpf_cpumask be cast to struct cpumask. */

	BUILD_BUG_ON(offsetof(struct bpf_cpumask, cpumask) != 0);



	cpumask = bpf_mem_alloc(&bpf_cpumask_ma, sizeof(*cpumask));

	if (!cpumask)

		return NULL;