linux-kernel - [PATCH 1/1] swiotlb: fix out-of-bounds TLB allocations with CONFIG_SWIOTLB

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Date:   Wed,  8 Nov 2023 12:12:49 +0100
From:   Petr Tesarik <petrtesarik@...weicloud.com>
To:     Christoph Hellwig <hch@....de>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Robin Murphy <robin.murphy@....com>,
        Petr Tesarik <petr.tesarik.ext@...wei.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        iommu@...ts.linux.dev (open list:DMA MAPPING HELPERS),
        linux-kernel@...r.kernel.org (open list)
Cc:     Wangkefeng <wangkefeng.wang@...wei.com>,
        Roberto Sassu <roberto.sassu@...weicloud.com>,
        petr@...arici.cz, Petr Tesarik <petr.tesarik1@...wei-partners.com>,
        Niklas Schnelle <schnelle@...ux.ibm.com>,
        Halil Pasic <pasic@...ux.ibm.com>, stable@...r.kernel.org
Subject: [PATCH 1/1] swiotlb: fix out-of-bounds TLB allocations with CONFIG_SWIOTLB_DYNAMIC

From: Petr Tesarik <petr.tesarik1@...wei-partners.com>

Limit the free list length to the size of the IO TLB. Transient pool can be
smaller than IO_TLB_SEGSIZE, but the free list is initialized with the
assumption that the total number of slots is a multiple of IO_TLB_SEGSIZE.
As a result, swiotlb_area_find_slots() may allocate slots past the end of
a transient IO TLB buffer.

Reported-by: Niklas Schnelle <schnelle@...ux.ibm.com>
Closes: https://lore.kernel.org/linux-iommu/104a8c8fedffd1ff8a2890983e2ec1c26bff6810.camel@linux.ibm.com/
Fixes: 79636caad361 ("swiotlb: if swiotlb is full, fall back to a transient memory pool")
Cc: Halil Pasic <pasic@...ux.ibm.com>
Cc: stable@...r.kernel.org
Signed-off-by: Petr Tesarik <petr.tesarik1@...wei-partners.com>
---
 kernel/dma/swiotlb.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 26202274784f..ec82524ba902 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -283,7 +283,8 @@ static void swiotlb_init_io_tlb_pool(struct io_tlb_pool *mem, phys_addr_t start,
 	}
 
 	for (i = 0; i < mem->nslabs; i++) {
-		mem->slots[i].list = IO_TLB_SEGSIZE - io_tlb_offset(i);
+		mem->slots[i].list = min(IO_TLB_SEGSIZE - io_tlb_offset(i),
+					 mem->nslabs - i);
 		mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
 		mem->slots[i].alloc_size = 0;
 	}
-- 
2.42.1