Re: [Qemu-devel] [PATCH v4 5/5] migration: Use strnlen() for fixed-size string

[Richard Henderson <richard.henderson@linaro.org>]

On 12/29/18 4:33 AM, Philippe Mathieu-Daudé wrote:
> GCC 8 introduced the -Wstringop-overflow, which detect buffer overflow
> by string-modifying functions declared in <string.h>, such strncpy(),
> used in global_state_store_running().
> 
> GCC indeed found an incorrect use of strlen(), because this array
> is loaded by VMSTATE_BUFFER(runstate, GlobalState) then parsed
> using qapi_enum_parse which does not get the buffer length.
> 
> Use strnlen() which returns sizeof(s->runstate) if the array is not
> NUL-terminated, assert the size is within range, and enforce the array
> to be NUL-terminated to avoid an overflow in qapi_enum_parse().
> 
> This fixes:
> 
>     CC      migration/global_state.o
>   qemu/migration/global_state.c: In function 'global_state_pre_save':
>   qemu/migration/global_state.c:109:15: error: 'strlen' argument 1 declared attribute 'nonstring' [-Werror=stringop-overflow=]
>        s->size = strlen((char *)s->runstate) + 1;
>                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~
>   qemu/migration/global_state.c:24:13: note: argument 'runstate' declared here
>        uint8_t runstate[100] QEMU_NONSTRING;
>                ^~~~~~~~
>   cc1: all warnings being treated as errors
>   make: *** [qemu/rules.mak:69: migration/global_state.o] Error 1
> 
> Suggested-by: Michael S. Tsirkin <mst@redhat.com>
> Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
> ---
>  migration/global_state.c | 13 ++++++++++++-
>  1 file changed, 12 insertions(+), 1 deletion(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~