bpf: remove obsolete KMALLOC_MAX_SIZE restriction on array map value size

Syscall-side map_lookup_elem() and map_update_elem() used to use
kmalloc() to allocate temporary buffers of value_size, so
KMALLOC_MAX_SIZE limit on value_size made sense to prevent creation of
array map that won't be accessible through syscall interface.

But this limitation since has been lifted by relying on kvmalloc() in
syscall handling code. So remove KMALLOC_MAX_SIZE, which among other
things means that it's possible to have BPF global variable sections
(.bss, .data, .rodata) bigger than 8MB now. Keep the sanity check to
prevent trivial overflows like round_up(map->value_size, 8) and restrict
value size to <= INT_MAX (2GB).

Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/r/20220715053146.1291891-4-andrii@kernel.org
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/arraymap.c b/kernel/bpf/arraymap.c
index 98ee09155151fc640c89337134e99b1a4ca44cf1..d3e734bf805692feaa466fe3e50ab2d7a95e7cb6 100644 (file)
--- a/kernel/bpf/arraymap.c
+++ b/kernel/bpf/arraymap.c
@@ -70,10 +70,8 @@ int array_map_alloc_check(union bpf_attr *attr)
            attr->map_flags & BPF_F_PRESERVE_ELEMS)
                return -EINVAL;
 
-       if (attr->value_size > KMALLOC_MAX_SIZE)
-               /* if value_size is bigger, the user space won't be able to
-                * access the elements.
-                */
+       /* avoid overflow on round_up(map->value_size) */
+       if (attr->value_size > INT_MAX)
                return -E2BIG;
 
        return 0;