[libvirt] [PATCH] conf: initialize character pointer xml value to avoid random crash

[Michal Prívozník]

On 07/05/2018 06:34 AM, Luyao Huang wrote:
> If the code jump to the cleanup before assagin value to xml pointer,
> libvirtd may get crashed when try to free an uninitialized pointer.
> 
> backtrace:
> 
> 0  0x00007ffff428d59c in free () from /lib64/libc.so.6
> 1  0x00007ffff721314a in virFree (ptrptr=ptrptr at entry=0x7fffc67f1b00) at util/viralloc.c:582
> 2  0x00007ffff7345ac4 in virDomainConfNWFilterInstantiate (vmname=<optimized out>,
>    vmuuid=vmuuid at entry=0x7fffc0181ca8 "߉\237\\۔H\262\206z\340\302f\265\233z", net=<optimized out>,
>    ignoreExists=ignoreExists at entry=true) at conf/domain_nwfilter.c:122
> 3  0x00007fffca5a77f6 in qemuProcessFiltersInstantiate (ignoreExists=true, def=0x7fffc0181ca0) at qemu/qemu_process.c:3028
> 4  qemuProcessReconnect (opaque=<optimized out>) at qemu/qemu_process.c:7653
> 5  0x00007ffff72c4895 in virThreadHelper (data=<optimized out>) at util/virthread.c:206
> 6  0x00007ffff45dcdd5 in start_thread () from /lib64/libpthread.so.0
> 7  0x00007ffff4305ead in clone () from /lib64/libc.so.6
> 
> Signed-off-by: Luyao Huang <lhuang at redhat.com>
> ---
>  src/conf/domain_nwfilter.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/conf/domain_nwfilter.c b/src/conf/domain_nwfilter.c
> index 948b324..24b5f42 100644
> --- a/src/conf/domain_nwfilter.c
> +++ b/src/conf/domain_nwfilter.c
> @@ -90,7 +90,7 @@ virDomainConfNWFilterInstantiate(const char *vmname,
>      virConnectPtr conn = virGetConnectNWFilter();
>      virNWFilterBindingDefPtr def = NULL;
>      virNWFilterBindingPtr binding = NULL;
> -    char *xml;
> +    char *xml = NULL;
>      int ret = -1;
>  
>      VIR_DEBUG("vmname=%s portdev=%s filter=%s ignoreExists=%d",
> 

Slightly reworked the commit message, ACKed and pushed.

Michal