Dan Williams <dan.j.williams@xxxxxxxxx> writes:
> In the case where a dimm does not have any associated flush hints the
> ndrd->flush_wpq array may be uninitialized leading to crashes with the
> following signature:
>
> BUG: unable to handle kernel NULL pointer dereference at 0000000000000010
> IP: region_visible+0x10f/0x160 [libnvdimm]
>
> Call Trace:
> internal_create_group+0xbe/0x2f0
> sysfs_create_groups+0x40/0x80
> device_add+0x2d8/0x650
> nd_async_device_register+0x12/0x40 [libnvdimm]
> async_run_entry_fn+0x39/0x170
> process_one_work+0x212/0x6c0
> ? process_one_work+0x197/0x6c0
> worker_thread+0x4e/0x4a0
> kthread+0x10c/0x140
> ? process_one_work+0x6c0/0x6c0
> ? kthread_create_on_node+0x60/0x60
> ret_from_fork+0x31/0x40
Sorry for being dense, but I'm having a tough time connecting the dots,
here. How does region_visible trip over the missing (not uninitialized,
you're actually walking off the end of the structure) wpq_flush array?
Anyway, the fix looks valid.
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Thanks,
Jeff
>
> Cc: <stable@xxxxxxxxxxxxxxx>
> Fixes: f284a4f23752 ("libnvdimm: introduce nvdimm_flush() and nvdimm_has_flush()")
> Signed-off-by: Dan Williams <dan.j.williams@xxxxxxxxx>
> ---
> drivers/nvdimm/region_devs.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/nvdimm/region_devs.c b/drivers/nvdimm/region_devs.c
> index 8de5a04644a1..24abceda986a 100644
> --- a/drivers/nvdimm/region_devs.c
> +++ b/drivers/nvdimm/region_devs.c
> @@ -1000,17 +1000,20 @@ EXPORT_SYMBOL_GPL(nvdimm_flush);
> */
> int nvdimm_has_flush(struct nd_region *nd_region)
> {
> - struct nd_region_data *ndrd = dev_get_drvdata(&nd_region->dev);
> int i;
>
> /* no nvdimm == flushing capability unknown */
> if (nd_region->ndr_mappings == 0)
> return -ENXIO;
>
> - for (i = 0; i < nd_region->ndr_mappings; i++)
> - /* flush hints present, flushing required */
> - if (ndrd_get_flush_wpq(ndrd, i, 0))
> + for (i = 0; i < nd_region->ndr_mappings; i++) {
> + struct nd_mapping *nd_mapping = &nd_region->mapping[i];
> + struct nvdimm *nvdimm = nd_mapping->nvdimm;
> +
> + /* flush hints present / available */
> + if (nvdimm->num_flush)
> return 1;
> + }
>
> /*
> * The platform defines dimm devices without hints, assume
>
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