| Message ID | 20230128141537.100777-1-void@manifault.com (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | cb4a21ea592f5753ab54cd8688306cf6423783a8 |
| Delegated to: | BPF |
| Headers | show |
| Series | [bpf-next] bpf: Build-time assert that cpumask offset is zero | expand |
Hello: This patch was applied to bpf/bpf-next.git (master) by Alexei Starovoitov <ast@kernel.org>: On Sat, 28 Jan 2023 08:15:37 -0600 you wrote: > 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. > > [...] Here is the summary with links: - [bpf-next] bpf: Build-time assert that cpumask offset is zero https://git.kernel.org/bpf/bpf-next/c/cb4a21ea592f You are awesome, thank you!
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;
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> --- kernel/bpf/cpumask.c | 3 +++ 1 file changed, 3 insertions(+)