linux-kernel - Re: [PATCH] misc: pci_endpoint_test: Fix pci_endpoint_test

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Date:   Tue, 16 Aug 2022 12:27:12 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Shunsuke Mie <mie@...l.co.jp>
Cc:     Kishon Vijay Abraham I <kishon@...com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Krzysztof Wilczyński <kw@...ux.com>,
        Arnd Bergmann <arnd@...db.de>, linux-pci@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] misc: pci_endpoint_test: Fix
 pci_endpoint_test_{copy,write,read}() panic

On Tue, Aug 16, 2022 at 07:06:17PM +0900, Shunsuke Mie wrote:
> Although dma_map_single() doesn't permit zero length mapping, the each
> test functions called the function without zero checking.
> 
> 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 checkings the payload length if it is zero.
> 
> Fixes: 343dc693f7b7 ("misc: pci_endpoint_test: Prevent some integer overflows")
> Signed-off-by: Shunsuke Mie <mie@...l.co.jp>
> ---
>  drivers/misc/pci_endpoint_test.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/misc/pci_endpoint_test.c b/drivers/misc/pci_endpoint_test.c
> index 8f786a225dcf..d45426a73396 100644
> --- a/drivers/misc/pci_endpoint_test.c
> +++ b/drivers/misc/pci_endpoint_test.c
> @@ -364,7 +364,7 @@ static bool pci_endpoint_test_copy(struct pci_endpoint_test *test,
>  	}
>  
>  	size = param.size;
> -	if (size > SIZE_MAX - alignment)
> +	if (size > SIZE_MAX - alignment || !size)
>  		goto err;

Can we test size first?  And do it in the ioctl handler in one place so
you don't have to add it everywhere?

Or have a "validate all parameters" function that you do it in one
place?

Also, all of these ioctl handlers are wrong, they are returning "0" to
userspace if they fail, which is not correct at all.

thanks,

greg k-h