Re: [RHEL7 qemu-kvm PATCH 2/3] s390x: Fix vm name copy length

[Thomas Huth]

On 11/01/2021 13.10, Philippe Mathieu-Daudé wrote:
> Hi Miroslav,
>
> On 1/11/21 12:30 PM, mrezanin@redhat.com wrote:
> > From: Miroslav Rezanina <mrezanin@redhat.com>
> >
> > There are two cases when vm name is copied but closing \0 can be lost
> > in case name is too long (>=256 characters).
> >
> > Updating length to copy so there is space for closing \0.
> >
> > Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
> > ---
> >   target/s390x/kvm.c         | 2 +-
> >   target/s390x/misc_helper.c | 4 +++-
> >   2 files changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/target/s390x/kvm.c b/target/s390x/kvm.c
> > index b8385e6b95..2313b5727e 100644
> > --- a/target/s390x/kvm.c
> > +++ b/target/s390x/kvm.c
> > @@ -1918,7 +1918,7 @@ static void insert_stsi_3_2_2(S390CPU *cpu, __u64 addr, 
> > uint8_t ar)
> >        */
> >       if (qemu_name) {
> >           strncpy((char *)sysib.ext_names[0], qemu_name,
> > -                sizeof(sysib.ext_names[0]));
> > +                sizeof(sysib.ext_names[0]) - 1);
> >       } else {
> >           strcpy((char *)sysib.ext_names[0], "KVMguest");
> >       }
>
> What about using strpadcpy() instead?

Yes, strpadcpy is the better way here - this field has to be padded with 
zeroes, so doing "- 1" is wrong here.

 Thomas