Re: [PATCH] swiotlb: swiotlb_tbl_map_single() kernel BUG in iommu-helper.h:30

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Fri, Feb 26, 2021 at 12:43:07PM -0800, Brad Larson wrote:
> 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.

I am looking at the stable/for-linus-5.12 and what I sent out for
a GIT PULL and I believe this is already squashed in:

531 static int find_slots(struct device *dev, phys_addr_t orig_addr,                
532                 size_t alloc_size)                                              
533 {                                                                               
534         unsigned long boundary_mask = dma_get_seg_boundary(dev);                
535         dma_addr_t tbl_dma_addr =                                               
536                 phys_to_dma_unencrypted(dev, io_tlb_start) & boundary_mask;     
537         unsigned long max_slots = get_max_slots(boundary_mask);

Could you double-check please?

> 
> [    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
>