bpf: cap BPF_PROG_PACK_SIZE to 2MB * num_possible_nodes()

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: ea2baba ("bpf: Simplify bpf_prog_pack_[size|mask]")
Reported-by: "kernelci.org bot" <[email protected]>
Closes: https://lore.kernel.org/all/[email protected]/
Suggested-by: Song Liu <[email protected]>
Signed-off-by: Puranjay Mohan <[email protected]>
Acked-by: Song Liu <[email protected]>
Message-ID: <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>

Author: puranjaymohan

kernel/bpf/core.c

@@ -893,8 +893,16 @@ 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