[PATCH bpf-next] bpf: cap BPF_PROG_PACK_SIZE to 2MB * num_possible_nodes()

[Puranjay Mohan]

On some architectures like ARM64, PMD_SIZE can be really large in some
configurations. Like with CONFIG_ARM64_64K_PAGES=y the PMD_SIZE is
512MB.

Use 2MB * num_possible_nodes() as the upper limit for allocations done
through the prog pack allocator.

Fixes: ea2babac63d4 ("bpf: Simplify bpf_prog_pack_[size|mask]")
Reported-by: "kernelci.org bot" <bot@xxxxxxxxxxxx>
Closes: https://lore.kernel.org/all/7e216c88-77ee-47b8-becc-a0f780868d3c@xxxxxxxxxxxxx/
Suggested-by: Song Liu <song@xxxxxxxxxx>
Signed-off-by: Puranjay Mohan <puranjay12@xxxxxxxxx>
---
 kernel/bpf/core.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c
index 134b7979f537..83a3b6964e54 100644
--- a/kernel/bpf/core.c
+++ b/kernel/bpf/core.c
@@ -893,8 +893,17 @@ static LIST_HEAD(pack_list);
  * CONFIG_MMU=n. Use PAGE_SIZE in these cases.
  */
 #ifdef PMD_SIZE
+/*
+ * PMD_SIZE is really big for some archs. It doesn't make sense to
+ * reserve too much memory in one allocation. Cap BPF_PROG_PACK_SIZE to
+ * 2MiB * num_possible_nodes().
+ */
+#if PMD_SIZE <= (1 << 21)
 #define BPF_PROG_PACK_SIZE (PMD_SIZE * num_possible_nodes())
 #else
+#define BPF_PROG_PACK_SIZE ((1 << 21) * num_possible_nodes())
+#endif
+#else
 #define BPF_PROG_PACK_SIZE PAGE_SIZE
 #endif
 
-- 
2.40.1