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From:   Brad Larson <brad@pensando.io>
To:     hch@lst.de, konrad.wilk@oracle.com, m.szyprowski@samsung.com,
        robin.murphy@arm.com, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
Cc:     Brad Larson <brad@pensando.io>
Subject: [PATCH] swiotlb: swiotlb_tbl_map_single() kernel BUG in iommu-helper.h:30
Date:   Fri, 26 Feb 2021 12:43:07 -0800
Message-Id: <20210226204307.50413-1-brad@pensando.io>
Precedence: bulk

Kernel Oops introduced in next-20210222 due to get_max_slots return arg size.
In the function find_slots() variable max_slots is zero when boundary_mask is
0xffffffffffffffff.

[    0.242119] kernel BUG at ./include/linux/iommu-helper.h:30!
[    0.247793] Internal error: Oops - BUG: 0 [#1] SMP
[    0.252595] Modules linked in:
[    0.255657] CPU: 0 PID: 93 Comm: kworker/0:1 Not tainted 5.11.0-next-20210224+ #25
[    0.263245] Hardware name: Elba ASIC Board (DT)
[    0.267784] Workqueue: events_freezable mmc_rescan
[    0.272592] pstate: 60000085 (nZCv daIf -PAN -UAO -TCO BTYPE=--)
[    0.278612] pc : swiotlb_tbl_map_single+0x2b0/0x6a0
[    0.283505] lr : swiotlb_tbl_map_single+0x440/0x6a0
[    0.288395] sp : ffffffc0122736b0
[    0.291713] x29: ffffffc0122736b0 x28: ffffffc010e30000
[    0.297039] x27: 00000000bbf58000 x26: 0000000000000000
[    0.302364] x25: 0000000000000000 x24: 0000000000000001
[    0.307689] x23: 0000000000000000 x22: 0000000000000000
[    0.313013] x21: 0000000000000000 x20: 0000000000000000
[    0.318338] x19: 0000001241fd4600 x18: ffffffc010d288c8
[    0.323662] x17: 0000000000000007 x16: 0000000000000001
[    0.328987] x15: ffffffc092273367 x14: 3a424c54204f4920
[    0.334311] x13: 6572617774666f73 x12: 20726e2030207865
[    0.339636] x11: 646e692078787820 x10: 3062653737317830
[    0.344960] x9 : 2074666968732031 x8 : ffffff977cf82368
[    0.350285] x7 : 0000000000000001 x6 : c0000000ffffefff
[    0.355609] x5 : 0000000000017fe8 x4 : 0000000000000000
[    0.360934] x3 : 0000000000000000 x2 : 18b0d50da009d000
[    0.366258] x1 : 0000000000000000 x0 : 0000000000000042
[    0.371583] Call trace:
[    0.374032]  swiotlb_tbl_map_single+0x2b0/0x6a0
[    0.378573]  swiotlb_map+0xa8/0x2b0

Signed-off-by: Brad Larson <brad@pensando.io>
---
 kernel/dma/swiotlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
index 369e4c3a0f2b..c10e855a03bc 100644
--- a/kernel/dma/swiotlb.c
+++ b/kernel/dma/swiotlb.c
@@ -534,7 +534,7 @@ static int find_slots(struct device *dev, phys_addr_t orig_addr,
 	unsigned long boundary_mask = dma_get_seg_boundary(dev);
 	dma_addr_t tbl_dma_addr =
 		phys_to_dma_unencrypted(dev, io_tlb_start) & boundary_mask;
-	unsigned int max_slots = get_max_slots(boundary_mask);
+	unsigned long max_slots = get_max_slots(boundary_mask);
 	unsigned int iotlb_align_mask =
 		dma_get_min_align_mask(dev) & ~(IO_TLB_SIZE - 1);
 	unsigned int nslots = nr_slots(alloc_size), stride;
-- 
2.17.1