[PATCH v2] iommu/amd: fix a crash in iova_magazine_free_pfns

[PATCH v2] iommu/amd: fix a crash in iova_magazine_free_pfns

[Qian Cai]

The commit b3aa14f02254 ("iommu: remove the mapping_error dma_map_ops
method") incorrectly changed the checking from dma_ops_alloc_iova() in
map_sg() causes a crash under memory pressure as dma_ops_alloc_iova()
never return DMA_MAPPING_ERROR on failure but 0, so the error handling
is all wrong.

   kernel BUG at drivers/iommu/iova.c:801!
    Workqueue: kblockd blk_mq_run_work_fn
    RIP: 0010:iova_magazine_free_pfns+0x7d/0xc0
    Call Trace:
     free_cpu_cached_iovas+0xbd/0x150
     alloc_iova_fast+0x8c/0xba
     dma_ops_alloc_iova.isra.6+0x65/0xa0
     map_sg+0x8c/0x2a0
     scsi_dma_map+0xc6/0x160
     pqi_aio_submit_io+0x1f6/0x440 [smartpqi]
     pqi_scsi_queue_command+0x90c/0xdd0 [smartpqi]
     scsi_queue_rq+0x79c/0x1200
     blk_mq_dispatch_rq_list+0x4dc/0xb70
     blk_mq_sched_dispatch_requests+0x249/0x310
     __blk_mq_run_hw_queue+0x128/0x200
     blk_mq_run_work_fn+0x27/0x30
     process_one_work+0x522/0xa10
     worker_thread+0x63/0x5b0
     kthread+0x1d2/0x1f0
     ret_from_fork+0x22/0x40

Fixes: b3aa14f02254 ("iommu: remove the mapping_error dma_map_ops method")
Signed-off-by: Qian Cai <cai@lca.pw>
---

v2: Fix the offensive commit directly.

 drivers/iommu/amd_iommu.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index 73740b969e62..b607a92791d3 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -2533,7 +2533,7 @@ static int map_sg(struct device *dev, struct scatterlist *sglist,
 	npages = sg_num_pages(dev, sglist, nelems);
 
 	address = dma_ops_alloc_iova(dev, dma_dom, npages, dma_mask);
-	if (address == DMA_MAPPING_ERROR)
+	if (!address)
 		goto out_err;
 
 	prot = dir2prot(direction);
-- 
1.8.3.1

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Re: [PATCH v2] iommu/amd: fix a crash in iova_magazine_free_pfns

[Christoph Hellwig]

Thanks, the change looks good to me:

Reviewed-by: Christoph Hellwig <hch@lst.de>
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Re: [PATCH v2] iommu/amd: fix a crash in iova_magazine_free_pfns

[Linus Torvalds]

On Thu, Jul 11, 2019 at 9:18 AM Qian Cai <cai@lca.pw> wrote:
>
> The commit b3aa14f02254 ("iommu: remove the mapping_error dma_map_ops
> method") incorrectly changed the checking from dma_ops_alloc_iova() in
> map_sg() causes a crash under memory pressure as dma_ops_alloc_iova()
> never return DMA_MAPPING_ERROR on failure but 0, so the error handling
> is all wrong.

This one seems to have fallen through the cracks.

Applied directly.

Maybe it's hiding in some fixes tree that I haven't gotten a pull
request for yet?

           Linus
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Re: [PATCH v2] iommu/amd: fix a crash in iova_magazine_free_pfns

[Joerg Roedel]

Hi Linus,

On Sun, Jul 21, 2019 at 09:58:04AM -0700, Linus Torvalds wrote:
> This one seems to have fallen through the cracks.
> 
> Applied directly.

Thanks!

> Maybe it's hiding in some fixes tree that I haven't gotten a pull
> request for yet?

No, I havn't had it applied anywhere yet. I usually don't pay close
attention to patches sent to me during the merge window, as I won't
update my tree anyway before -rc1.

I only take care of important fixes, but this one seems to have
fallen through my heuristic. Thanks for applying it directly.


Regards,

	Joerg
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