Re: [PATCH] system/physmem: Silence warning from ubsan

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

Cc'ing Patrick & Peter for similar patch:
https://lore.kernel.org/qemu-devel/aCUDxEQVACn5CY8f@x1.local/

On 28/7/25 19:25, Thomas Huth wrote:
> From: Thomas Huth <thuth@redhat.com>
> 
> When compiling QEMU with --enable-ubsan there is a undefined behavior
> warning when running the bios-tables-test for example:
> 
>   .../system/physmem.c:3243:13: runtime error: applying non-zero offset 262144 to null pointer
>      #0 0x55ac1df5fbc4 in address_space_write_rom_internal .../system/physmem.c:3243:13
> 
> The problem is that buf is indeed NULL if the function is e.g. called
> with type == FLUSH_CACHE. Add a check to fix the issue.
> 
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>   system/physmem.c | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/system/physmem.c b/system/physmem.c
> index 130c148ffb5..00333ffa7f7 100644
> --- a/system/physmem.c
> +++ b/system/physmem.c
> @@ -3240,8 +3240,10 @@ static inline MemTxResult address_space_write_rom_internal(AddressSpace *as,
>               }
>           }
>           len -= l;
> -        buf += l;
>           addr += l;
> +        if (buf) {
> +            buf += l;
> +        }
>       }
>       return MEMTX_OK;
>   }