From 463e862ac63ef27fca423782536f6465abc3f180 Mon Sep 17 00:00:00 2001 From: Will Deacon Date: Tue, 20 Jul 2021 14:38:24 +0100 Subject: swiotlb: Convert io_default_tlb_mem to static allocation Since commit 69031f500865 ("swiotlb: Set dev->dma_io_tlb_mem to the swiotlb pool used"), 'struct device' may hold a copy of the global 'io_default_tlb_mem' pointer if the device is using swiotlb for DMA. A subsequent call to swiotlb_exit() will therefore leave dangling pointers behind in these device structures, resulting in KASAN splats such as: | BUG: KASAN: use-after-free in __iommu_dma_unmap_swiotlb+0x64/0xb0 | Read of size 8 at addr ffff8881d7830000 by task swapper/0/0 | | CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.12.0-rc3-debug #1 | Hardware name: HP HP Desktop M01-F1xxx/87D6, BIOS F.12 12/17/2020 | Call Trace: | | dump_stack+0x9c/0xcf | print_address_description.constprop.0+0x18/0x130 | kasan_report.cold+0x7f/0x111 | __iommu_dma_unmap_swiotlb+0x64/0xb0 | nvme_pci_complete_rq+0x73/0x130 | blk_complete_reqs+0x6f/0x80 | __do_softirq+0xfc/0x3be Convert 'io_default_tlb_mem' to a static structure, so that the per-device pointers remain valid after swiotlb_exit() has been invoked. All users are updated to reference the static structure directly, using the 'nslabs' field to determine whether swiotlb has been initialised. The 'slots' array is still allocated dynamically and referenced via a pointer rather than a flexible array member. Cc: Claire Chang Cc: Christoph Hellwig Cc: Robin Murphy Cc: Konrad Rzeszutek Wilk Fixes: 69031f500865 ("swiotlb: Set dev->dma_io_tlb_mem to the swiotlb pool used") Reported-by: Nathan Chancellor Tested-by: Nathan Chancellor Tested-by: Claire Chang Reviewed-by: Christoph Hellwig Signed-off-by: Will Deacon Signed-off-by: Konrad Rzeszutek Wilk --- drivers/xen/swiotlb-xen.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'drivers/xen') diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c index 785ec7e8be01..f06d9b4f1e0f 100644 --- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -164,7 +164,7 @@ int __ref xen_swiotlb_init(void) int rc = -ENOMEM; char *start; - if (io_tlb_default_mem != NULL) { + if (io_tlb_default_mem.nslabs) { pr_warn("swiotlb buffer already initialized\n"); return -EEXIST; } @@ -547,7 +547,7 @@ xen_swiotlb_sync_sg_for_device(struct device *dev, struct scatterlist *sgl, static int xen_swiotlb_dma_supported(struct device *hwdev, u64 mask) { - return xen_phys_to_dma(hwdev, io_tlb_default_mem->end - 1) <= mask; + return xen_phys_to_dma(hwdev, io_tlb_default_mem.end - 1) <= mask; } const struct dma_map_ops xen_swiotlb_dma_ops = { -- cgit v1.2.3