From 9be2fa205c9e1337a68847ae38e791bd6b17cc42 Mon Sep 17 00:00:00 2001 From: Michael Holzheu Date: Thu, 12 May 2016 18:10:48 +0200 Subject: [PATCH] s390/bpf: reduce maximum program size to 64 KB commit 0fa963553a5c28d8f8aabd8878326d3f782045fc upstream. The s390 BFP compiler currently uses relative branch instructions that only support jumps up to 64 KB. Examples are "j", "jnz", "cgrj", etc. Currently the maximum size of s390 BPF programs is set to 0x7ffff. If branches over 64 KB are generated the, kernel can crash due to incorrect code. So fix this an reduce the maximum size to 64 KB. Programs larger than that will be interpreted. Fixes: ce2b6ad9c185 ("s390/bpf: increase BPF_SIZE_MAX") Signed-off-by: Michael Holzheu Signed-off-by: Martin Schwidefsky Signed-off-by: Greg Kroah-Hartman --- arch/s390/net/bpf_jit_comp.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/s390/net/bpf_jit_comp.c b/arch/s390/net/bpf_jit_comp.c index fe607c8d25d2..0e2919dd8df3 100644 --- a/arch/s390/net/bpf_jit_comp.c +++ b/arch/s390/net/bpf_jit_comp.c @@ -45,7 +45,7 @@ struct bpf_jit { int labels[1]; /* Labels for local jumps */ }; -#define BPF_SIZE_MAX 0x7ffff /* Max size for program (20 bit signed displ) */ +#define BPF_SIZE_MAX 0xffff /* Max size for program (16 bit branches) */ #define SEEN_SKB 1 /* skb access */ #define SEEN_MEM 2 /* use mem[] for temporary storage */ -- 2.39.2