avoid endless loops in lib/swiotlb.c
Commit 681cc5cd3efbeafca6386114070e0bfb5012e249 ("iommu sg merging:
swiotlb: respect the segment boundary limits") introduced two
possibilities for entering an endless loop in lib/swiotlb.c:
- if max_slots is zero (possible if mask is ~0UL)
- if the number of slots requested fits into a swiotlb segment, but is
too large for the part of a segment which remains after considering
offset_slots
This fixes them
Signed-off-by: Jan Beulich <jbeulich@novell.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/lib/swiotlb.c b/lib/swiotlb.c
index 4bb5a11..0259228 100644
--- a/lib/swiotlb.c
+++ b/lib/swiotlb.c
@@ -310,7 +310,9 @@
start_dma_addr = virt_to_bus(io_tlb_start) & mask;
offset_slots = ALIGN(start_dma_addr, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
- max_slots = ALIGN(mask + 1, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT;
+ max_slots = mask + 1
+ ? ALIGN(mask + 1, 1 << IO_TLB_SHIFT) >> IO_TLB_SHIFT
+ : 1UL << (BITS_PER_LONG - IO_TLB_SHIFT);
/*
* For mappings greater than a page, we limit the stride (and
@@ -333,16 +335,18 @@
index = ALIGN(io_tlb_index, stride);
if (index >= io_tlb_nslabs)
index = 0;
-
- while (is_span_boundary(index, nslots, offset_slots,
- max_slots)) {
- index += stride;
- if (index >= io_tlb_nslabs)
- index = 0;
- }
wrap = index;
do {
+ while (is_span_boundary(index, nslots, offset_slots,
+ max_slots)) {
+ index += stride;
+ if (index >= io_tlb_nslabs)
+ index = 0;
+ if (index == wrap)
+ goto not_found;
+ }
+
/*
* If we find a slot that indicates we have 'nslots'
* number of contiguous buffers, we allocate the
@@ -367,14 +371,12 @@
goto found;
}
- do {
- index += stride;
- if (index >= io_tlb_nslabs)
- index = 0;
- } while (is_span_boundary(index, nslots, offset_slots,
- max_slots));
+ index += stride;
+ if (index >= io_tlb_nslabs)
+ index = 0;
} while (index != wrap);
+ not_found:
spin_unlock_irqrestore(&io_tlb_lock, flags);
return NULL;
}