Re: [RFC PATCH v2 2/2] misc: pci_endpoint_test: Fix pci_endpoint_test_{copy,write,read}() panic

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Tue, Sep 06, 2022 at 07:15:55PM +0900, Shunsuke Mie wrote:
> The dma_map_single() doesn't permit zero length mapping. It causes a follow
> panic.
> 
> A panic was reported on arm64:
> 
> [   60.137988] ------------[ cut here ]------------
> [   60.142630] kernel BUG at kernel/dma/swiotlb.c:624!
> [   60.147508] Internal error: Oops - BUG: 0 [#1] PREEMPT SMP
> [   60.152992] Modules linked in: dw_hdmi_cec crct10dif_ce simple_bridge rcar_fdp1 vsp1 rcar_vin videobuf2_vmalloc rcar_csi2 v4l
> 2_mem2mem videobuf2_dma_contig videobuf2_memops pci_endpoint_test videobuf2_v4l2 videobuf2_common rcar_fcp v4l2_fwnode v4l2_asyn
> c videodev mc gpio_bd9571mwv max9611 pwm_rcar ccree at24 authenc libdes phy_rcar_gen3_usb3 usb_dmac display_connector pwm_bl
> [   60.186252] CPU: 0 PID: 508 Comm: pcitest Not tainted 6.0.0-rc1rpci-dev+ #237
> [   60.193387] Hardware name: Renesas Salvator-X 2nd version board based on r8a77951 (DT)
> [   60.201302] pstate: 00000005 (nzcv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
> [   60.208263] pc : swiotlb_tbl_map_single+0x2c0/0x590
> [   60.213149] lr : swiotlb_map+0x88/0x1f0
> [   60.216982] sp : ffff80000a883bc0
> [   60.220292] x29: ffff80000a883bc0 x28: 0000000000000000 x27: 0000000000000000
> [   60.227430] x26: 0000000000000000 x25: ffff0004c0da20d0 x24: ffff80000a1f77c0
> [   60.234567] x23: 0000000000000002 x22: 0001000040000010 x21: 000000007a000000
> [   60.241703] x20: 0000000000200000 x19: 0000000000000000 x18: 0000000000000000
> [   60.248840] x17: 0000000000000000 x16: 0000000000000000 x15: ffff0006ff7b9180
> [   60.255977] x14: ffff0006ff7b9180 x13: 0000000000000000 x12: 0000000000000000
> [   60.263113] x11: 0000000000000000 x10: 0000000000000000 x9 : 0000000000000000
> [   60.270249] x8 : 0001000000000010 x7 : ffff0004c6754b20 x6 : 0000000000000000
> [   60.277385] x5 : ffff0004c0da2090 x4 : 0000000000000000 x3 : 0000000000000001
> [   60.284521] x2 : 0000000040000000 x1 : 0000000000000000 x0 : 0000000040000010
> [   60.291658] Call trace:
> [   60.294100]  swiotlb_tbl_map_single+0x2c0/0x590
> [   60.298629]  swiotlb_map+0x88/0x1f0
> [   60.302115]  dma_map_page_attrs+0x188/0x230
> [   60.306299]  pci_endpoint_test_ioctl+0x5e4/0xd90 [pci_endpoint_test]
> [   60.312660]  __arm64_sys_ioctl+0xa8/0xf0
> [   60.316583]  invoke_syscall+0x44/0x108
> [   60.320334]  el0_svc_common.constprop.0+0xcc/0xf0
> [   60.325038]  do_el0_svc+0x2c/0xb8
> [   60.328351]  el0_svc+0x2c/0x88
> [   60.331406]  el0t_64_sync_handler+0xb8/0xc0
> [   60.335587]  el0t_64_sync+0x18c/0x190
> [   60.339251] Code: 52800013 d2e00414 35fff45c d503201f (d4210000)
> [   60.345344] ---[ end trace 0000000000000000 ]---
> 
> To fix it, this patch adds a checking the payload length if it is zero.
> 
> Fixes: 343dc693f7b7 ("misc: pci_endpoint_test: Prevent some integer overflows")
> Signed-off-by: Shunsuke Mie <mie@igel.co.jp>
> ---
> Changes in v2:
> * Move a checking code to an introduced function in previous patch
> ---
> ---
>  drivers/misc/pci_endpoint_test.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
> index 3bd9f135cdac..a7193bf6a49f 100644
> --- a/drivers/misc/pci_endpoint_test.c
> +++ b/drivers/misc/pci_endpoint_test.c
> @@ -335,6 +335,11 @@ static bool pci_endpoint_test_msi_irq(struct pci_endpoint_test *test,
>  static int pci_endpoint_test_validate_xfer_params(struct device *dev,
>  		struct pci_endpoint_test_xfer_param *param, size_t alignment)
>  {
> +	if (!param->size) {
> +		dev_err(dev, "Data size is zero\n");

Again, do not allow userspace to spam the kernel log.

thanks,

greg k-h