[Qemu-devel] Re: [RFT][PATCH 01/15] hpet: Catch out-of-bounds timer access

[Jan Kiszka <jan.kiszka@web.de>]

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Juan Quintela wrote:
> Jan Kiszka <jan.kiszka@web.de> wrote:
>> From: Jan Kiszka <jan.kiszka@siemens.com>
>>
>> Also prevent out-of-bounds write access to the timers but don't spam the
>> host console if it triggers.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
>> ---
>>  hw/hpet.c |    6 +++++-
>>  1 files changed, 5 insertions(+), 1 deletions(-)
>>
>> diff --git a/hw/hpet.c b/hw/hpet.c
>> index 8729fb2..1980906 100644
>> --- a/hw/hpet.c
>> +++ b/hw/hpet.c
>> @@ -294,7 +294,7 @@ static uint32_t hpet_ram_readl(void *opaque, target_phys_addr_t addr)
>>      if (index >= 0x100 && index <= 0x3ff) {
>>          uint8_t timer_id = (addr - 0x100) / 0x20;
>>          if (timer_id > HPET_NUM_TIMERS - 1) {
>> -            printf("qemu: timer id out of range\n");
>> +            DPRINTF("qemu: timer id out of range\n");
>>              return 0;
>>          }
>>          HPETTimer *timer = &s->timer[timer_id];
>> @@ -383,6 +383,10 @@ static void hpet_ram_writel(void *opaque, target_phys_addr_t addr,
>>          DPRINTF("qemu: hpet_ram_writel timer_id = %#x \n", timer_id);
> 
> if you are going to check timer_id, check it before accessing the array?

That's just address arithmetic, nothing is dereferenced at this point.

Jan


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