From: Daniel Borkmann <daniel@iogearbox.net>
Date: Sat, 19 Aug 2017 03:12:45 +0200
Subject: bpf: make htab inlining more robust wrt assumptions
Patch-mainline: v4.14-rc1
Git-commit: 89c63074c2bc25874e4e72406ff15a9a8e3df750
References: bsc#1056787

Commit 9015d2f59535 ("bpf: inline htab_map_lookup_elem()") was
making the assumption that a direct call emission to the function
__htab_map_lookup_elem() will always work out for JITs.

This is currently true since all JITs we have are for 64 bit archs,
but in case of 32 bit JITs like upcoming arm32, we get a NULL pointer
dereference when executing the call to __htab_map_lookup_elem()
since passed arguments are of a different size (due to pointer args)
than what we do out of BPF. Guard and thus limit this for now for
the current 64 bit JITs only.

Reported-by: Shubham Bansal <illusionist.neo@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 kernel/bpf/verifier.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c
@@ -4142,7 +4142,11 @@ static int fixup_bpf_calls(struct bpf_ve
 			continue;
 		}
 
-		if (ebpf_jit_enabled() && insn->imm == BPF_FUNC_map_lookup_elem) {
+		/* BPF_EMIT_CALL() assumptions in some of the map_gen_lookup
+		 * handlers are currently limited to 64 bit only.
+		 */
+		if (ebpf_jit_enabled() && BITS_PER_LONG == 64 &&
+		    insn->imm == BPF_FUNC_map_lookup_elem) {
 			map_ptr = env->insn_aux_data[i + delta].map_ptr;
 			if (map_ptr == BPF_MAP_PTR_POISON ||
 			    !map_ptr->ops->map_gen_lookup)