Re: [PATCH] target/microblaze: Fix possible array out of bounds in mmu_write()

[Philippe Mathieu-Daudé]

On 11/3/20 8:46 AM, AlexChen wrote:
> The size of env->mmu.regs is 3, but the range of 'rn' is [0, 5].
> To avoid data access out of bounds, only if 'rn' is less than 3, we
> can print env->mmu.regs[rn]. In other cases, we can print
> env->mmu.regs[MMU_R_TLBX].
> 
> Reported-by: Euler Robot <euler.robot@huawei.com>
> Signed-off-by: Alex Chen <alex.chen@huawei.com>
> ---
>  target/microblaze/mmu.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/target/microblaze/mmu.c b/target/microblaze/mmu.c
> index 1dbbb271c4..917ad6d69e 100644
> --- a/target/microblaze/mmu.c
> +++ b/target/microblaze/mmu.c
> @@ -234,7 +234,8 @@ void mmu_write(CPUMBState *env, bool ext, uint32_t rn, 
> uint32_t v)
>      unsigned int i;
> 
>      qemu_log_mask(CPU_LOG_MMU,
> -                  "%s rn=%d=%x old=%x\n", __func__, rn, v, 
> env->mmu.regs[rn]);
> +                  "%s rn=%d=%x old=%x\n", __func__, rn, v,
> +                  rn < 3 ? env->mmu.regs[rn] : env->mmu.regs[MMU_R_TLBX]);

Nack. If rn >= ARRAY_SIZE(env->mmu.regs), then don't displays it.
Else it is confuse to see a value unrelated to the MMU index used...

> 
>      if (cpu->cfg.mmu < 2 || !cpu->cfg.mmu_tlb_access) {
>          qemu_log_mask(LOG_GUEST_ERROR, "MMU access on MMU-less system\n");
>