mov %rsp, %r1 ; r1 = rsp add $-8, %r1 ; r1 = rsp - 8 store_q $123, -8(%rsp) ; *(u64*)r1 = 123 <- valid store_q $123, (%r1) ; *(u64*)r1 = 123 <- previously invalid mov $0, %r0 exit ; Always need to exit
And we'd get the following error: 0: (bf) r1 = r10 1: (07) r1 += -8 2: (7a) *(u64 *)(r10 -8) = 999 3: (7a) *(u64 *)(r1 +0) = 999 R1 invalid mem access 'fp' Unable to load program We already know that a register is a stack address and the appropriate offset, so we should be able to validate those references as well. Signed-off-by: Alex Gartrell <agartr...@fb.com> --- kernel/bpf/verifier.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c index 039d866..5dfbece 100644 --- a/kernel/bpf/verifier.c +++ b/kernel/bpf/verifier.c @@ -676,6 +676,15 @@ static int check_mem_access(struct verifier_env *env, u32 regno, int off, err = check_stack_write(state, off, size, value_regno); else err = check_stack_read(state, off, size, value_regno); + } else if (state->regs[regno].type == PTR_TO_STACK) { + int real_off = state->regs[regno].imm + off; + + if (t == BPF_WRITE) + err = check_stack_write( + state, real_off, size, value_regno); + else + err = check_stack_read( + state, real_off, size, value_regno); } else { verbose("R%d invalid mem access '%s'\n", regno, reg_type_str[state->regs[regno].type]); -- Alex Gartrell <agartr...@fb.com> -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html