From e01f09149d2dc540c0ef1c0bec48c45cd592ec14 Mon Sep 17 00:00:00 2001 From: Paul Burton Date: Fri, 1 Mar 2019 22:58:09 +0000 Subject: [PATCH] MIPS: eBPF: Fix icache flush end address commit d1a2930d8a992fb6ac2529449f81a0056e1b98d1 upstream. The MIPS eBPF JIT calls flush_icache_range() in order to ensure the icache observes the code that we just wrote. Unfortunately it gets the end address calculation wrong due to some bad pointer arithmetic. The struct jit_ctx target field is of type pointer to u32, and as such adding one to it will increment the address being pointed to by 4 bytes. Therefore in order to find the address of the end of the code we simply need to add the number of 4 byte instructions emitted, but we mistakenly add the number of instructions multiplied by 4. This results in the call to flush_icache_range() operating on a memory region 4x larger than intended, which is always wasteful and can cause crashes if we overrun into an unmapped page. Fix this by correcting the pointer arithmetic to remove the bogus multiplication, and use braces to remove the need for a set of brackets whilst also making it obvious that the target field is a pointer. Signed-off-by: Paul Burton Fixes: b6bd53f9c4e8 ("MIPS: Add missing file for eBPF JIT.") Cc: Alexei Starovoitov Cc: Daniel Borkmann Cc: Martin KaFai Lau Cc: Song Liu Cc: Yonghong Song Cc: netdev@vger.kernel.org Cc: bpf@vger.kernel.org Cc: linux-mips@vger.kernel.org Cc: stable@vger.kernel.org # v4.13+ Signed-off-by: Daniel Borkmann Signed-off-by: Greg Kroah-Hartman --- arch/mips/net/ebpf_jit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/mips/net/ebpf_jit.c b/arch/mips/net/ebpf_jit.c index dd537cba4449..8004bfcfb033 100644 --- a/arch/mips/net/ebpf_jit.c +++ b/arch/mips/net/ebpf_jit.c @@ -1971,7 +1971,7 @@ struct bpf_prog *bpf_int_jit_compile(struct bpf_prog *prog) /* Update the icache */ flush_icache_range((unsigned long)ctx.target, - (unsigned long)(ctx.target + ctx.idx * sizeof(u32))); + (unsigned long)&ctx.target[ctx.idx]); if (bpf_jit_enable > 1) /* Dump JIT code */ -- 2.20.1