[PATCH v2] Handle out-of-memory case in svc_tcp.c/svc_unix.c:rendezvous_request.

[Adhemerval Zanella]

On 04/12/2020 13:00, Stefan Liebler via Libc-alpha wrote:
> If glibc is build with -O3 on at least 390 (-m31) or x86 (-m32),
> gcc 11 dumps this warning:
> svc_tcp.c: In function 'rendezvous_request':
> svc_tcp.c:274:3: error: 'memcpy' offset [0, 15] is out of the bounds [0, 0] [-Werror=array-bounds]
>   274 |   memcpy (&xprt->xp_raddr, &addr, sizeof (addr));
>       |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> cc1: all warnings being treated as errors
> 
> In out-of-memory case, if one of the mallocs in makefd_xprt function
> returns NULL, a message is dumped, makefd_xprt returns NULL
> and the subsequent memcpy would copy to NULL.
> 
> Instead of a segfaulting, we delay a bit (see also __svc_accept_failed
> and Bug 14889 (CVE-2011-4609) - svc_run() produces high cpu usage when
> accept() fails with EMFILE (CVE-2011-4609).
> 
> The same applies to svc_unix.c.

LGTM, thanks.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

> ---
>  include/rpc/svc.h |  1 +
>  sunrpc/svc.c      | 10 ++++++++--
>  sunrpc/svc_tcp.c  |  8 ++++++++
>  sunrpc/svc_unix.c |  8 ++++++++
>  4 files changed, 25 insertions(+), 2 deletions(-)
> 
> diff --git a/include/rpc/svc.h b/include/rpc/svc.h
> index 465bf4427d..d9c0e8fbca 100644
> --- a/include/rpc/svc.h
> +++ b/include/rpc/svc.h
> @@ -38,6 +38,7 @@ libc_hidden_proto (svc_getreq_common)
>  libc_hidden_proto (svc_getreq_poll)
>  
>  extern void __svc_accept_failed (void) attribute_hidden;
> +extern void __svc_wait_on_error (void) attribute_hidden;
>  
>  # endif /* !_ISOMAC */
>  #endif

Ok.

> diff --git a/sunrpc/svc.c b/sunrpc/svc.c
> index 917e9a311c..3ed6cee09e 100644
> --- a/sunrpc/svc.c
> +++ b/sunrpc/svc.c
> @@ -545,6 +545,13 @@ svc_getreq_common (const int fd)
>  }
>  libc_hidden_nolink_sunrpc (svc_getreq_common, GLIBC_2_2)
>  
> +void
> +__svc_wait_on_error (void)
> +{
> +  struct timespec ts = { .tv_sec = 0, .tv_nsec = 50000000 };
> +  __nanosleep (&ts, NULL);
> +}
> +
>  /* If there are no file descriptors available, then accept will fail.
>     We want to delay here so the connection request can be dequeued;
>     otherwise we can bounce between polling and accepting, never giving the

Ok.

> @@ -555,8 +562,7 @@ __svc_accept_failed (void)
>  {
>    if (errno == EMFILE)
>      {
> -      struct timespec ts = { .tv_sec = 0, .tv_nsec = 50000000 };
> -      __nanosleep (&ts, NULL);
> +      __svc_wait_on_error ();
>      }
>  }
>  

Ok.

> diff --git a/sunrpc/svc_tcp.c b/sunrpc/svc_tcp.c
> index efbdd22548..12de60f605 100644
> --- a/sunrpc/svc_tcp.c
> +++ b/sunrpc/svc_tcp.c
> @@ -271,6 +271,14 @@ again:
>     * make a new transporter (re-uses xprt)
>     */
>    xprt = makefd_xprt (sock, r->sendsize, r->recvsize);
> +
> +  /* If we are out of memory, makefd_xprt has already dumped an error.  */
> +  if (xprt == NULL)
> +    {
> +      __svc_wait_on_error ();
> +      return FALSE;
> +    }
> +
>    memcpy (&xprt->xp_raddr, &addr, sizeof (addr));
>    xprt->xp_addrlen = len;
>    return FALSE;		/* there is never an rpc msg to be processed */

Ok.

> diff --git a/sunrpc/svc_unix.c b/sunrpc/svc_unix.c
> index e01afeabe6..3decea427c 100644
> --- a/sunrpc/svc_unix.c
> +++ b/sunrpc/svc_unix.c
> @@ -270,6 +270,14 @@ again:
>    memset (&in_addr, '\0', sizeof (in_addr));
>    in_addr.sin_family = AF_UNIX;
>    xprt = makefd_xprt (sock, r->sendsize, r->recvsize);
> +
> +  /* If we are out of memory, makefd_xprt has already dumped an error.  */
> +  if (xprt == NULL)
> +    {
> +      __svc_wait_on_error ();
> +      return FALSE;
> +    }
> +
>    memcpy (&xprt->xp_raddr, &in_addr, sizeof (in_addr));
>    xprt->xp_addrlen = len;
>    return FALSE;		/* there is never an rpc msg to be processed */
> 

Ok.