Re: [libvirt] [PATCH] Fix latent buffer overflow in qemudOpenMonitorUnix.

["Daniel P. Berrange" <berrange redhat com>]

On Fri, Jul 31, 2009 at 03:20:09PM +0200, Chris Lalancette wrote:
> Fix a possible latent bug in qemudOpenMonitorUnix().  If the pathname
> to the monitor is very long (i.e. >= UNIX_MAX_PATH), then strncpy will
> *not* place a final \0 on the string (see "man strncpy").
> NULL terminate the buffer to ensure we don't run off the end.
> 
> Signed-off-by: Chris Lalancette <clalance redhat com>
> ---
>  src/qemu_driver.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/src/qemu_driver.c b/src/qemu_driver.c
> index 9fcc07a..4f173b7 100644
> --- a/src/qemu_driver.c
> +++ b/src/qemu_driver.c
> @@ -910,6 +910,7 @@ qemudOpenMonitorUnix(virConnectPtr conn,
>      memset(&addr, 0, sizeof(addr));
>      addr.sun_family = AF_UNIX;
>      strncpy(addr.sun_path, monitor, sizeof(addr.sun_path));
> +    NUL_TERMINATE(addr.sun_path);
>  
>      do {
>          ret = connect(monfd, (struct sockaddr *) &addr, sizeof(addr));

ACK, but this mistake is made in pretty much every use of unix 
domain sockets :-( Could you fix the others here too.


Clearly strncpy() is just unfit for purpose, and we should plan to banish
it in favour of a virStrncpy impl that guarnetees to add the trailing \0.

Daniel
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