Le 12/08/2020 à 19:08, Greg Kurz a écrit :
> Since commit 61f20b9dc5b7 ("spapr_nvram: Pre-initialize the NVRAM to
> support the -prom-env parameter"), pseries machines can pre-initialize
> the "system" partition in the NVRAM with the data passed to all -prom-env
> parameters on the QEMU command line.
>
> In this cases it is assumed that all the data fits in 64 KiB, but the user
> can easily pass more and crash QEMU:
>
> $ qemu-system-ppc64 -M pseries $(for ((x=0;x<128;x++)); do \
> echo -n " -prom-env "$(for ((y=0;y<1024;y++)); do echo -n x ; done) ; \
> done) # this requires ~128 Kib
> malloc(): corrupted top size
> Aborted (core dumped)
>
> Call chrp_nvram_create_system_partition() first, with its recently added
> parameter dry_run set to true, in order to know the required size and fail
> gracefully if it's too small.
Why do you need the dry_run parameter?
Can't you fail on the normal case?
Thanks,
Laurent
>
> Reported-by: John Snow <js...@redhat.com>
> Signed-off-by: Greg Kurz <gr...@kaod.org>
> ---
> hw/nvram/spapr_nvram.c | 15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
> diff --git a/hw/nvram/spapr_nvram.c b/hw/nvram/spapr_nvram.c
> index 992b818d34e7..c29d797ae1f0 100644
> --- a/hw/nvram/spapr_nvram.c
> +++ b/hw/nvram/spapr_nvram.c
> @@ -145,6 +145,7 @@ static void rtas_nvram_store(PowerPCCPU *cpu,
> SpaprMachineState *spapr,
>
> static void spapr_nvram_realize(SpaprVioDevice *dev, Error **errp)
> {
> + ERRP_GUARD();
> SpaprNvram *nvram = VIO_SPAPR_NVRAM(dev);
> int ret;
>
> @@ -187,6 +188,20 @@ static void spapr_nvram_realize(SpaprVioDevice *dev,
> Error **errp)
> return;
> }
> } else if (nb_prom_envs > 0) {
> + int len = chrp_nvram_create_system_partition(nvram->buf,
> + MIN_NVRAM_SIZE / 4,
> + true);
> +
> + /* Check the partition is large enough for all the -prom-env data */
> + if (nvram->size < len) {
> + error_setg(errp, "-prom-env data requires %d bytes but
> spapr-nvram "
> + "is only %d bytes in size", len, nvram->size);
> + error_append_hint(errp,
> + "Try to pass %d less bytes to -prom-env.\n",
> + len - nvram->size);
> + return;
> + }
> +
> /* Create a system partition to pass the -prom-env variables */
> chrp_nvram_create_system_partition(nvram->buf, MIN_NVRAM_SIZE / 4,
> false);
>
>
