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Re: [libvirt] [PATCH 4/4] rpc: Fix potentially segfaults



On Thu, Feb 09, 2017 at 03:13 PM +0100, Marc Hartmayer <mhartmay linux vnet ibm com> wrote:
> We have to allocate first and if, and only if, it was successful we
> can set the count. A segfault has occurred in
> virNetServerServiceNewPostExecRestart() when VIR_ALLOC_N(svc->socks,
> n) has failed, but svc->nsocsk = n was already set. Thus
> virObejectUnref(svc) was called and therefore it was possible that
> virNetServerServiceDispose was called => segmentation fault.  For
> safeness NULL pointer check were added in
> virNetServerServiceDispose().
>
> Signed-off-by: Marc Hartmayer <mhartmay linux vnet ibm com>
> Reviewed-by: Boris Fiuczynski <fiuczy linux vnet ibm com>
> Reviewed-by: Bjoern Walk <bwalk linux vnet ibm com>
> ---
>  src/rpc/virnetserverservice.c | 20 +++++++++++---------
>  1 file changed, 11 insertions(+), 9 deletions(-)
>
> diff --git a/src/rpc/virnetserverservice.c b/src/rpc/virnetserverservice.c
> index 1ef0636..006d041 100644
> --- a/src/rpc/virnetserverservice.c
> +++ b/src/rpc/virnetserverservice.c
> @@ -228,9 +228,9 @@ virNetServerServicePtr virNetServerServiceNewUNIX(const char *path,
>      svc->tls = virObjectRef(tls);
>  #endif
>
> -    svc->nsocks = 1;
> -    if (VIR_ALLOC_N(svc->socks, svc->nsocks) < 0)
> +    if (VIR_ALLOC_N(svc->socks, 1) < 0)
>          goto error;
> +    svc->nsocks = 1;
>
>      if (virNetSocketNewListenUNIX(path,
>                                    mask,
> @@ -289,9 +289,9 @@ virNetServerServicePtr virNetServerServiceNewFD(int fd,
>      svc->tls = virObjectRef(tls);
>  #endif
>
> -    svc->nsocks = 1;
> -    if (VIR_ALLOC_N(svc->socks, svc->nsocks) < 0)
> +    if (VIR_ALLOC_N(svc->socks, 1) < 0)
>          goto error;
> +    svc->nsocks = 1;
>
>      if (virNetSocketNewListenFD(fd,
>                                  &svc->socks[0]) < 0)
> @@ -367,9 +367,9 @@ virNetServerServicePtr virNetServerServiceNewPostExecRestart(virJSONValuePtr obj
>          goto error;
>      }
>
> -    svc->nsocks = n;
> -    if (VIR_ALLOC_N(svc->socks, svc->nsocks) < 0)
> +    if (VIR_ALLOC_N(svc->socks, n) < 0)
>          goto error;
> +    svc->nsocks = n;
>
>      for (i = 0; i < svc->nsocks; i++) {
>          virJSONValuePtr child = virJSONValueArrayGet(socks, i);
> @@ -492,9 +492,11 @@ void virNetServerServiceDispose(void *obj)
>      virNetServerServicePtr svc = obj;
>      size_t i;
>
> -    for (i = 0; i < svc->nsocks; i++)
> -        virObjectUnref(svc->socks[i]);
> -    VIR_FREE(svc->socks);
> +    if (svc->socks) {
> +        for (i = 0; i < svc->nsocks; i++)
> +            virObjectUnref(svc->socks[i]);
> +        VIR_FREE(svc->socks);

Should we set svc->nsocks = 0 instead of using a NULL-pointer check (or
do both)?

> +    }
>
>  #if WITH_GNUTLS
>      virObjectUnref(svc->tls);
> --
> 2.5.5
>
--
Beste Grüße / Kind regards
   Marc Hartmayer

IBM Deutschland Research & Development GmbH
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschäftsführung: Dirk Wittkopp
Sitz der Gesellschaft: Böblingen
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