ACPI: sysfs: Map only the requested range in acpi_data_show()

acpi_data_show() maps the whole data region on every read(), although
it copies at most count bytes and sysfs passes at most PAGE_SIZE bytes
per call. acpi_os_unmap_iomem() defers the iounmap until after an RCU
grace period, so a process reading one of these files in a loop keeps
many full-size mappings in flight.

Map only the range being read. acpi_os_map_iomem() rounds the mapping
to page boundaries, so each mapping is now at most two pages, whatever
the size of the region.

A malformed table can describe a region that wraps around the end of
the physical address space. acpi_os_map_iomem() doesn't check for that,
and its lookup of existing mappings then matches an unrelated mapping,
with or without this change. Fail reads of such a region before mapping
anything.

Signed-off-by: Jamie Nguyen <jamien@nvidia.com>
Link: https://patch.msgid.link/20261013180728.957618-1-jamien@nvidia.com
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

0 files changed, 0 insertions, 0 deletions