x86/mm: Fix overflow in __cpa_addr()

The change to have cpa_flush() call flush_kernel_pages() introduced
a bug where __cpa_addr() can access an address one larger than the
largest one in the cpa->pages array.

KASAN reports the issue like this:

BUG: KASAN: slab-out-of-bounds in __cpa_addr arch/x86/mm/pat/set_memory.c:309 [inline]
BUG: KASAN: slab-out-of-bounds in __cpa_addr+0x1d3/0x220 arch/x86/mm/pat/set_memory.c:306
Read of size 8 at addr ffff88801f75e8f8 by task syz.0.17/5978

This bug could cause cpa_flush() to not properly flush memory,
which somehow never showed any symptoms in my tests, possibly
because cpa_flush() is called so rarely, but could potentially
cause issues for other people.

Fix the issue by directly calculating the flush end address
from the start address.

Fixes: 86e6815b316e ("x86/mm: Change cpa_flush() to call flush_kernel_range() directly")
Reported-by: [email protected]
Signed-off-by: Rik van Riel <[email protected]>
Signed-off-by: Dave Hansen <[email protected]>
Reviewed-by: Kiryl Shutsemau <[email protected]>
Link: https://lore.kernel.org/all/[email protected]/

0 files changed, 0 insertions, 0 deletions