[PATCH v2 0/1] mm/memory: constrain generic_access_phys() to page boundary

[Ren Wei <weir@nebusec.ai>]

From: Luxiao Xu <rakukuip@gmail.com>

Hi all,

This is v2 of the fix for generic_access_phys() out-of-bounds mapping.

In v1, we attempted to handle multi-page ranges by adding an internal
chunk loop inside generic_access_phys(). Following feedback from David
Hildenbrand, we realized that caller (__access_remote_vm) already has an
outer loop and handles normal pages chunk-by-chunk.

Instead of duplicating the loop logic in generic_access_phys(), v2
clamps the access length passed to ->access() in __access_remote_vm() to
not cross the page boundary (PAGE_SIZE - offset_in_page(addr)). Because
all VMAs are page-aligned, this also naturally ensures accesses never
cross VMA boundaries. Each page access is then driven by the outer loop,
looking up the VMA and resolving PFN/protections per page.

Additionally, we fixed the missing (resource_size_t) cast in PFN
comparison as pointed out by Andrew Morton.

Thanks,
Luxiao / Ren Wei

Luxiao Xu (1):
  mm/memory: constrain generic_access_phys() to page boundary

 mm/memory.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

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2.43.0