Re: [PATCH 1/2] migration: avoid suspicious strncpy() use

[Philippe Mathieu-Daudé]

On 3/16/20 5:07 PM, Stefan Hajnoczi wrote:
> gcc (GCC) 9.2.1 20190827 (Red Hat 9.2.1-1) with sanitizers enabled
> reports the following error:
>
>      CC      migration/global_state.o
>    In file included from /usr/include/string.h:495,
>                     from /home/stefanha/qemu/include/qemu/osdep.h:101,
>                     from migration/global_state.c:13:
>    In function ‘strncpy’,
>        inlined from ‘global_state_store_running’ at 
> migration/global_state.c:47:5:
>    /usr/include/bits/string_fortified.h:106:10: error: ‘__builtin_strncpy’ 
> specified bound 100 equals destination size [-Werror=stringop-truncation]
>      106 |   return __builtin___strncpy_chk (__dest, __src, __len, __bos 
> (__dest));
>          |          
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> Use pstrcpy() instead of strncpy().  It is guaranteed to NUL-terminate
> strings.

There was a long discussion 1 year ago with it, and Eric suggested to 
use strpadcpy after the assert() and I sent this patch:
https://www.mail-archive.com/address@hidden/msg44925.html
Not sure what's best.

> Signed-off-by: Stefan Hajnoczi <address@hidden>
> ---
>   migration/global_state.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/migration/global_state.c b/migration/global_state.c
> index 25311479a4..cbe07f21a8 100644
> --- a/migration/global_state.c
> +++ b/migration/global_state.c
> @@ -44,8 +44,8 @@ void global_state_store_running(void)
>   {
>       const char *state = RunState_str(RUN_STATE_RUNNING);
>       assert(strlen(state) < sizeof(global_state.runstate));
> -    strncpy((char *)global_state.runstate,
> -           state, sizeof(global_state.runstate));
> +    pstrcpy((char *)global_state.runstate,
> +            sizeof(global_state.runstate), state);
>   }
>   
>   bool global_state_received(void)