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authorDavid Vernet <void@manifault.com>2023-01-28 15:15:37 +0100
committerAlexei Starovoitov <ast@kernel.org>2023-01-28 21:21:40 +0100
commitcb4a21ea592f5753ab54cd8688306cf6423783a8 (patch)
treefdcc4ac5a343d517505452918798e38615e8e097 /kernel/bpf
parentnet: netlink: recommend policy range validation (diff)
downloadlinux-cb4a21ea592f5753ab54cd8688306cf6423783a8.tar.xz
linux-cb4a21ea592f5753ab54cd8688306cf6423783a8.zip
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: David Vernet <void@manifault.com> Link: https://lore.kernel.org/r/20230128141537.100777-1-void@manifault.com Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Diffstat (limited to 'kernel/bpf')
-rw-r--r--kernel/bpf/cpumask.c3
1 files changed, 3 insertions, 0 deletions
diff --git a/kernel/bpf/cpumask.c b/kernel/bpf/cpumask.c
index 25355a0a367a..6bbb67dfc998 100644
--- a/kernel/bpf/cpumask.c
+++ b/kernel/bpf/cpumask.c
@@ -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;