[PATCH bpf-next] bpf: Do not alloc arena on unsupported arches

[Viktor Malik <vmalik@redhat.com>]

Do not allocate BPF arena on arches that do not support it, instead
return EOPNOTSUPP. This is useful to prevent bugs such as soft lockups
while trying to free the arena which we have witnessed on ppc64le [1].

[1] https://lore.kernel.org/bpf/4afdcb50-13f2-4772-8db1-3fd02bd985b3@redhat.com/

Signed-off-by: Viktor Malik <vmalik@redhat.com>
---
 kernel/bpf/arena.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/kernel/bpf/arena.c b/kernel/bpf/arena.c
index 3e1dfe349ced..945a5680f6a5 100644
--- a/kernel/bpf/arena.c
+++ b/kernel/bpf/arena.c
@@ -3,6 +3,7 @@
 #include <linux/bpf.h>
 #include <linux/btf.h>
 #include <linux/err.h>
+#include "linux/filter.h"
 #include <linux/btf_ids.h>
 #include <linux/vmalloc.h>
 #include <linux/pagemap.h>
@@ -99,6 +100,9 @@ static struct bpf_map *arena_map_alloc(union bpf_attr *attr)
 	u64 vm_range;
 	int err = -ENOMEM;
 
+	if (!bpf_jit_supports_arena())
+		return ERR_PTR(-EOPNOTSUPP);
+
 	if (attr->key_size || attr->value_size || attr->max_entries == 0 ||
 	    /* BPF_F_MMAPABLE must be set */
 	    !(attr->map_flags & BPF_F_MMAPABLE) ||
-- 
2.47.0