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Commit b15a3891 authored by Jan Beulich's avatar Jan Beulich Committed by Linus Torvalds
Browse files

avoid endless loops in lib/swiotlb.c 



Commit 681cc5cd ("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: default avatarJan Beulich <jbeulich@novell.com>
Cc: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 96e31022

lib/swiotlb.c

+16 −14
Original line number Diff line number Diff line
@@ -310,7 +310,9 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir) 
	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 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir) 
		index = ALIGN(io_tlb_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;

			}

		wrap = index;



		do {

			/*

			 * If we find a slot that indicates we have 'nslots'

			 * number of contiguous buffers, we allocate the
@@ -367,14 +371,12 @@ map_single(struct device *hwdev, char *buffer, size_t size, int dir) 


				goto found;

			}

			do {

			index += stride;

			if (index >= io_tlb_nslabs)

				index = 0;

			} while (is_span_boundary(index, nslots, offset_slots,

						  max_slots));

		} while (index != wrap);



  not_found:

		spin_unlock_irqrestore(&io_tlb_lock, flags);

		return NULL;

	}