Apparently, struct bpf_empty_prog_array exists entirely to populate a single element of "items" in a global variable. "null_prog" is only used during the initializer.
None of this is needed; globals will be correctly sized with an array initializer of a flexible-array member. So, remove struct bpf_empty_prog_array and adjust the rest of the code, accordingly. With these changes, fix the following warnings: 7659 ./include/linux/bpf.h:2369:31: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end] Signed-off-by: Gustavo A. R. Silva <[email protected]> --- Changes in v2: - Remove struct bpf_empty_prog_array. (Kees) v1: -Link: https://lore.kernel.org/linux-hardening/aaZr2A1UPJq33127@kspp/ include/linux/bpf-cgroup.h | 2 +- include/linux/bpf.h | 7 +------ kernel/bpf/core.c | 12 +++++++----- 3 files changed, 9 insertions(+), 12 deletions(-) diff --git a/include/linux/bpf-cgroup.h b/include/linux/bpf-cgroup.h index 2f535331f926..b2e79c2b41d5 100644 --- a/include/linux/bpf-cgroup.h +++ b/include/linux/bpf-cgroup.h @@ -184,7 +184,7 @@ static inline bool cgroup_bpf_sock_enabled(struct sock *sk, struct bpf_prog_array *array; array = rcu_access_pointer(cgrp->bpf.effective[type]); - return array != &bpf_empty_prog_array.hdr; + return array != &bpf_empty_prog_array; } /* Wrappers for __cgroup_bpf_run_filter_skb() guarded by cgroup_bpf_enabled. */ diff --git a/include/linux/bpf.h b/include/linux/bpf.h index 05b34a6355b0..4f5b9e85a20c 100644 --- a/include/linux/bpf.h +++ b/include/linux/bpf.h @@ -2365,18 +2365,13 @@ struct bpf_prog_array { struct bpf_prog_array_item items[]; }; -struct bpf_empty_prog_array { - struct bpf_prog_array hdr; - struct bpf_prog *null_prog; -}; - /* to avoid allocating empty bpf_prog_array for cgroups that * don't have bpf program attached use one global 'bpf_empty_prog_array' * It will not be modified the caller of bpf_prog_array_alloc() * (since caller requested prog_cnt == 0) * that pointer should be 'freed' by bpf_prog_array_free() */ -extern struct bpf_empty_prog_array bpf_empty_prog_array; +extern struct bpf_prog_array bpf_empty_prog_array; struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags); void bpf_prog_array_free(struct bpf_prog_array *progs); diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c index 67eb12b637a5..ca39d2e690b9 100644 --- a/kernel/bpf/core.c +++ b/kernel/bpf/core.c @@ -2613,8 +2613,10 @@ static struct bpf_prog_dummy { }, }; -struct bpf_empty_prog_array bpf_empty_prog_array = { - .null_prog = NULL, +struct bpf_prog_array bpf_empty_prog_array = { + .items = { + { .prog = NULL }, + }, }; EXPORT_SYMBOL(bpf_empty_prog_array); @@ -2625,14 +2627,14 @@ struct bpf_prog_array *bpf_prog_array_alloc(u32 prog_cnt, gfp_t flags) if (prog_cnt) p = kzalloc_flex(*p, items, prog_cnt + 1, flags); else - p = &bpf_empty_prog_array.hdr; + p = &bpf_empty_prog_array; return p; } void bpf_prog_array_free(struct bpf_prog_array *progs) { - if (!progs || progs == &bpf_empty_prog_array.hdr) + if (!progs || progs == &bpf_empty_prog_array) return; kfree_rcu(progs, rcu); } @@ -2653,7 +2655,7 @@ static void __bpf_prog_array_free_sleepable_cb(struct rcu_head *rcu) void bpf_prog_array_free_sleepable(struct bpf_prog_array *progs) { - if (!progs || progs == &bpf_empty_prog_array.hdr) + if (!progs || progs == &bpf_empty_prog_array) return; call_rcu_tasks_trace(&progs->rcu, __bpf_prog_array_free_sleepable_cb); } -- 2.43.0
