On 10/23/15, Nathan Fontenot <nf...@linux.vnet.ibm.com> wrote:
> When DLPAR adding a CPU we should verify that the CPU does not already
> exist. Failure to do so can generate a kernel oops;
>
> [ 9.465585] kernel BUG at arch/powerpc/platforms/pseries/dlpar.c:382!
> [ 9.465796] Oops: Exception in kernel mode, sig: 5 [#1]
>
> This oops can be generated by causing a probe to be performed on a cpu
> by writing to the sysfs cpu probe file (/sys/devices/system/cpu/probe).
> This patch adds a check for the existence of cpu prior to probing the cpu
> so userspace doing the wrong thing won't trigger a BUG_ON().
Hi Nathan,
Can you please tell how to trigger the oops manually since I've tried to write
a core number to the probe file, but with no luck. Always get -EINVAL.
Thanks!
>
> Signed-off-by: Nathan Fontenot <nf...@linux.vnet.ibm.com>
> ---
> arch/powerpc/platforms/pseries/dlpar.c | 43
> +++++++++++++++++++++++++++++---
> 1 file changed, 39 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/platforms/pseries/dlpar.c
> b/arch/powerpc/platforms/pseries/dlpar.c
> index f244dcb..fe6320d 100644
> --- a/arch/powerpc/platforms/pseries/dlpar.c
> +++ b/arch/powerpc/platforms/pseries/dlpar.c
> @@ -381,6 +381,32 @@ out:
>
> }
>
> +static bool dlpar_cpu_exists(struct device_node *parent, u32 drc_index)
> +{
> + struct device_node *child = NULL;
> + u32 my_drc_index;
> + bool found;
> + int rc;
> +
> + /* Assume cpu doesn't exist */
> + found = false;
> +
> + for_each_child_of_node(parent, child) {
> + rc = of_property_read_u32(child, "ibm,my-drc-index",
> + &my_drc_index);
> + if (rc)
> + continue;
> +
> + if (my_drc_index == drc_index) {
> + of_node_put(child);
> + found = true;
> + break;
> + }
> + }
> +
> + return found;
> +}
> +
> static ssize_t dlpar_cpu_probe(const char *buf, size_t count)
> {
> struct device_node *dn, *parent;
> @@ -391,14 +417,23 @@ static ssize_t dlpar_cpu_probe(const char *buf, size_t
> count)
> if (rc)
> return -EINVAL;
>
> - rc = dlpar_acquire_drc(drc_index);
> - if (rc)
> - return -EINVAL;
> -
> parent = of_find_node_by_path("/cpus");
> if (!parent)
> return -ENODEV;
>
> + if (dlpar_cpu_exists(parent, drc_index)) {
> + of_node_put(parent);
> + printk(KERN_WARNING "CPU with drc index %x already exists\n",
> + drc_index);
> + return -EINVAL;
> + }
> +
> + rc = dlpar_acquire_drc(drc_index);
> + if (rc) {
> + of_node_put(parent);
> + return -EINVAL;
> + }
> +
> dn = dlpar_configure_connector(cpu_to_be32(drc_index), parent);
> of_node_put(parent);
> if (!dn) {
>
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