Re: [Qemu-devel] [PATCH v3 4/8] s390x: Dump storage keys qmp command

[Eric Blake <eblake@redhat.com>]

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On 08/31/2015 05:00 AM, Cornelia Huck wrote:
> From: "Jason J. Herne" <jjherne@linux.vnet.ibm.com>
> 
> Provide a dump-skeys qmp command to allow the end user to dump storage
> keys. This is useful for debugging problems with guest storage key support
> within Qemu and for guest operating system developers.
> 
> Reviewed-by: Thomas Huth <thuth@linux.vnet.ibm.com>
> Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
> Signed-off-by: Jason J. Herne <jjherne@linux.vnet.ibm.com>
> Signed-off-by: Cornelia Huck <cornelia.huck@de.ibm.com>
> ---
>  hw/s390x/s390-skeys.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++--
>  monitor.c             |  7 ++++
>  qapi-schema.json      | 14 ++++++++
>  qmp-commands.hx       | 25 ++++++++++++++
>  4 files changed, 134 insertions(+), 2 deletions(-)
> 

> +static void write_keys(QEMUFile *f, uint8_t *keys, uint64_t startgfn,
> +                       uint64_t count, Error **errp)
> +{
> +    uint64_t curpage = startgfn;
> +    uint64_t maxpage = curpage + count - 1;
> +    const char *fmt = "page=%03" PRIx64 ": key(%d) => ACC=%X, FP=%d, REF=%d,"
> +                      " ch=%d, reserved=%d\n";
> +    char buf[128];
> +    int len;
> +
> +    for (; curpage <= maxpage; curpage++) {
> +        uint8_t acc = (*keys & 0xF0) >> 4;
> +        int fp =  (*keys & 0x08);
> +        int ref = (*keys & 0x04);
> +        int ch = (*keys & 0x02);
> +        int res = (*keys & 0x01);
> +
> +        len = snprintf(buf, sizeof(buf), fmt, curpage,
> +                       *keys, acc, fp, ref, ch, res);
> +        qemu_put_buffer(f, (uint8_t *)buf, len);

While I can overlook the use of snprintf(), I still think you ought to
at least have assert(len < sizeof(buf)) here before the
qemu_put_buffer(), to ensure that future changes to fmt don't attempt to
print beyond the end of the fixed-width buffer.

With an assert added,
Reviewed-by: Eric Blake <eblake@redhat.com>

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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