From: Colin Ian King <colin.king@canonical.com>
Date: Thu, 15 Jul 2021 13:57:12 +0100
Subject: s390/bpf: Perform r1 range checking before accessing
 jit->seen_reg[r1]
Git-commit: 91091656252f5d6d8c476e0c92776ce9fae7b445
Patch-mainline: v5.14-rc3
References: git-fixes

Currently array jit->seen_reg[r1] is being accessed before the range
checking of index r1. The range changing on r1 should be performed
first since it will avoid any potential out-of-range accesses on the
array seen_reg[] and also it is more optimal to perform checks on r1
before fetching data from the array. Fix this by swapping the order
of the checks before the array access.

Fixes: 054623105728 ("s390/bpf: Add s390x eBPF JIT compiler backend")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Tested-by: Ilya Leoshkevich <iii@linux.ibm.com>
Acked-by: Ilya Leoshkevich <iii@linux.ibm.com>
Link: https://lore.kernel.org/bpf/20210715125712.24690-1-colin.king@canonical.com

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 arch/s390/net/bpf_jit_comp.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/arch/s390/net/bpf_jit_comp.c
+++ b/arch/s390/net/bpf_jit_comp.c
@@ -115,7 +115,7 @@ static inline void reg_set_seen(struct b
 {
 	u32 r1 = reg2hex[b1];
 
-	if (!jit->seen_reg[r1] && r1 >= 6 && r1 <= 15)
+	if (r1 >= 6 && r1 <= 15 && !jit->seen_reg[r1])
 		jit->seen_reg[r1] = 1;
 }