From 8eee539ddea09bccae2426f09b0ba6a18b72b691 Mon Sep 17 00:00:00 2001 From: Xi Wang Date: Thu, 25 Jun 2015 05:47:39 -0700 Subject: arm64: bpf: fix out-of-bounds read in bpf2a64_offset() Problems occur when bpf_to or bpf_from has value prog->len - 1 (e.g., "Very long jump backwards" in test_bpf where the last instruction is a jump): since ctx->offset has length prog->len, ctx->offset[bpf_to + 1] or ctx->offset[bpf_from + 1] will cause an out-of-bounds read, leading to a bogus jump offset and kernel panic. This patch moves updating ctx->offset to after calling build_insn(), and changes indexing to use bpf_to and bpf_from without + 1. Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler") Cc: # 3.18+ Cc: Zi Shen Lim Cc: Will Deacon Acked-by: Alexei Starovoitov Signed-off-by: Xi Wang Signed-off-by: Catalin Marinas --- arch/arm64/net/bpf_jit_comp.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) (limited to 'arch/arm64/net') diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index dc6a4842683a..c81ddd4ff7f7 100644 --- a/arch/arm64/net/bpf_jit_comp.c +++ b/arch/arm64/net/bpf_jit_comp.c @@ -113,9 +113,9 @@ static inline void emit_a64_mov_i(const int is64, const int reg, static inline int bpf2a64_offset(int bpf_to, int bpf_from, const struct jit_ctx *ctx) { - int to = ctx->offset[bpf_to + 1]; + int to = ctx->offset[bpf_to]; /* -1 to account for the Branch instruction */ - int from = ctx->offset[bpf_from + 1] - 1; + int from = ctx->offset[bpf_from] - 1; return to - from; } @@ -640,10 +640,11 @@ static int build_body(struct jit_ctx *ctx) const struct bpf_insn *insn = &prog->insnsi[i]; int ret; + ret = build_insn(insn, ctx); + if (ctx->image == NULL) ctx->offset[i] = ctx->idx; - ret = build_insn(insn, ctx); if (ret > 0) { i++; continue; -- cgit v1.2.3-59-g8ed1b