Re: [PATCH] hw/s390x/s390-pci-bus.c: Use g_assert_not_reached() in functions taking an ett

[Halil Pasic <pasic@linux.ibm.com>]

On Thu, 10 Jul 2025 17:15:52 +0100
Peter Maydell <peter.maydell@linaro.org> wrote:

> The s390-pci-bus.c code, Coverity complains about a possible overflow
> because get_table_index() can return -1 if the ett value passed in is
> not one of the three permitted ZPCI_ETT_PT, ZPCI_ETT_ST, ZPCI_ETT_RT,
> but the caller in table_translate() doesn't check this and instead
> uses the return value directly in a calculation of the guest address
> to read from.
> 
> In fact this case cannot happen, because:
>  * get_table_index() is called only from table_translate()
>  * the only caller of table_translate() loops through the ett values
>    in the order RT, ST, PT until table_translate() returns 0
>  * table_translate() will return 0 for the error cases and when
>    translate_iscomplete() returns true
>  * translate_iscomplete() is always true for ZPCI_ETT_PT
> 
> So table_translate() is always called with a valid ett value.
> 
> Instead of having the various functions called from table_translate()
> return a default or dummy value when the ett argument is out of range,
> use g_assert_not_reached() to indicate that this is impossible.
> 
> Coverity: CID 1547609
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

Reviewed-by: Halil Pasic <pasic@linux.ibm.com>