| Message ID | 1435236459-15141-1-git-send-email-xi.wang@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 6/25/15 5:47 AM, Xi Wang wrote: > 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. > > Cc: Zi Shen Lim<zlim.lnx@gmail.com> > Cc: Alexei Starovoitov<ast@plumgrid.com> > Cc: Will Deacon<will.deacon@arm.com> > Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler") > Signed-off-by: Xi Wang<xi.wang@gmail.com> Nice catch! Looks good to me. Acked-by: Alexei Starovoitov <ast@plumgrid.com>
On Thu, Jun 25, 2015 at 05:47:39AM -0700, Xi Wang wrote: > 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. > > Cc: Zi Shen Lim <zlim.lnx@gmail.com> > Cc: Alexei Starovoitov <ast@plumgrid.com> > Cc: Will Deacon <will.deacon@arm.com> > Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler") > Signed-off-by: Xi Wang <xi.wang@gmail.com> Thanks. Applied.
diff --git a/arch/arm64/net/bpf_jit_comp.c b/arch/arm64/net/bpf_jit_comp.c index dc6a484..c81ddd4 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;
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. Cc: Zi Shen Lim <zlim.lnx@gmail.com> Cc: Alexei Starovoitov <ast@plumgrid.com> Cc: Will Deacon <will.deacon@arm.com> Fixes: e54bcde3d69d ("arm64: eBPF JIT compiler") Signed-off-by: Xi Wang <xi.wang@gmail.com> --- arch/arm64/net/bpf_jit_comp.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-)