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-rw-r--r--drivers/firmware/efi/libstub/random.c13
1 files changed, 7 insertions, 6 deletions
diff --git a/drivers/firmware/efi/libstub/random.c b/drivers/firmware/efi/libstub/random.c
index 3a3feacc329f..7e72954d5860 100644
--- a/drivers/firmware/efi/libstub/random.c
+++ b/drivers/firmware/efi/libstub/random.c
@@ -45,19 +45,20 @@ static unsigned long get_entry_num_slots(efi_memory_desc_t *md,
unsigned long align_shift)
{
unsigned long align = 1UL << align_shift;
- u64 start, end;
+ u64 first_slot, last_slot, region_end;
if (md->type != EFI_CONVENTIONAL_MEMORY)
return 0;
- start = round_up(md->phys_addr, align);
- end = round_down(md->phys_addr + md->num_pages * EFI_PAGE_SIZE - size,
- align);
+ region_end = min((u64)ULONG_MAX, md->phys_addr + md->num_pages*EFI_PAGE_SIZE - 1);
- if (start > end)
+ first_slot = round_up(md->phys_addr, align);
+ last_slot = round_down(region_end - size + 1, align);
+
+ if (first_slot > last_slot)
return 0;
- return (end - start + 1) >> align_shift;
+ return ((unsigned long)(last_slot - first_slot) >> align_shift) + 1;
}
/*