Re: [Qemu-devel] [PATCH] sd: Fix out-of-bounds assertions

[Liam Merwick <liam.merwick@oracle.com>]

On 09/04/2019 06:51, Markus Armbruster wrote:
> Lidong Chen <lidong.chen@oracle.com> writes:
>
>> Due to an off-by-one error, the assert statements allow an
>> out-of-bounds array access.
>>
>> Signed-off-by: Lidong Chen <lidong.chen@oracle.com>


Reviewed-by: Liam Merwick <liam.merwick@oracle.com>


>> ---
>>   hw/sd/sd.c | 4 ++--
>>   1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/sd/sd.c b/hw/sd/sd.c
>> index aaab15f..818f86c 100644
>> --- a/hw/sd/sd.c
>> +++ b/hw/sd/sd.c
>> @@ -144,7 +144,7 @@ static const char *sd_state_name(enum SDCardStates state)
>>       if (state == sd_inactive_state) {
>>           return "inactive";
>>       }
>> -    assert(state <= ARRAY_SIZE(state_name));
>> +    assert(state < ARRAY_SIZE(state_name));
>>       return state_name[state];
>>   }
>>   
>> @@ -165,7 +165,7 @@ static const char *sd_response_name(sd_rsp_type_t rsp)
>>       if (rsp == sd_r1b) {
>>           rsp = sd_r1;
>>       }
>> -    assert(rsp <= ARRAY_SIZE(response_name));
>> +    assert(rsp < ARRAY_SIZE(response_name));
>>       return response_name[rsp];
>>   }
> This is the second fix for this bug pattern in a fortnight.  Where's
> one, there are more:


As Lidong mentioned, an internal static analysis tool (Parfait) was used 
to catch these. Not every arch/board is compiled but I had eyeballed the 
code of most interest to me and they seemed fine (e.g. for array 
accesses, the subsequent loops used a less-than check)

However, this WIN32 code in util/main-loop.c seems wrong.

425     g_assert(n_poll_fds <= ARRAY_SIZE(poll_fds));
426
427     for (i = 0; i < w->num; i++) {
428         poll_fds[n_poll_fds + i].fd = (DWORD_PTR)w->events[i];
429         poll_fds[n_poll_fds + i].events = G_IO_IN;
430     }

Seems like this should be:

g_assert(n_poll_fds + w->num <= ARRAY_SIZE(poll_fds));

Otherwise, the rest seem fine.

Regards,

Liam


>
> $ git-grep '<= ARRAY_SIZE'
> hw/intc/arm_gicv3_cpuif.c:    assert(aprmax <= ARRAY_SIZE(cs->ich_apr[0]));
> hw/intc/arm_gicv3_cpuif.c:    assert(aprmax <= ARRAY_SIZE(cs->ich_apr[0]));
> hw/net/stellaris_enet.c:        if (s->tx_fifo_len + 4 <= ARRAY_SIZE(s->tx_fifo)) {
> hw/sd/pxa2xx_mmci.c:        && s->tx_len <= ARRAY_SIZE(s->tx_fifo)
> hw/sd/pxa2xx_mmci.c:        && s->rx_len <= ARRAY_SIZE(s->rx_fifo)
> hw/sd/pxa2xx_mmci.c:        && s->resp_len <= ARRAY_SIZE(s->resp_fifo);
> hw/sd/sd.c:    assert(state <= ARRAY_SIZE(state_name));
> hw/sd/sd.c:    assert(rsp <= ARRAY_SIZE(response_name));
> hw/usb/hcd-xhci.c:    assert(n <= ARRAY_SIZE(tmp));
> target/mips/op_helper.c:    if (base_reglist > 0 && base_reglist <= ARRAY_SIZE (multiple_regs)) {
> target/mips/op_helper.c:    if (base_reglist > 0 && base_reglist <= ARRAY_SIZE (multiple_regs)) {
> target/mips/op_helper.c:    if (base_reglist > 0 && base_reglist <= ARRAY_SIZE (multiple_regs)) {
> target/mips/op_helper.c:    if (base_reglist > 0 && base_reglist <= ARRAY_SIZE (multiple_regs)) {
> target/ppc/kvm.c:           <= ARRAY_SIZE(hw_debug_points));
> target/ppc/kvm.c:           <= ARRAY_SIZE(hw_debug_points));
> target/ppc/kvm.c:    assert((nb_hw_breakpoint + nb_hw_watchpoint) <= ARRAY_SIZE(dbg->arch.bp));
> tcg/tcg.c:    tcg_debug_assert(pi <= ARRAY_SIZE(op->args));
> util/main-loop.c:    g_assert(n_poll_fds <= ARRAY_SIZE(poll_fds));
> util/module.c:    assert(n_dirs <= ARRAY_SIZE(dirs));
>
> Lidong Chen, would you like to have a look at these?
>
> Cc'ing maintainers to help with further investigation.
>