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

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Date:   Wed, 17 Aug 2022 13:14:11 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Kishon Vijay Abraham I <kishon@...com>
Cc:     Lorenzo Pieralisi <lpieralisi@...nel.org>,
        Shunsuke Mie <mie@...l.co.jp>,
        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 Wed, Aug 17, 2022 at 02:18:58PM +0530, Kishon Vijay Abraham I wrote:
> Hi Lorenzo,
> 
> On 16/08/22 20:24, Lorenzo Pieralisi wrote:
> > On Tue, Aug 16, 2022 at 12:27:12PM +0200, Greg Kroah-Hartman wrote:
> >> 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.
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/tools/pci/pcitest.c
> > This is bad, thanks Greg for spotting it.
> > 
> > @Kishon, we have to fix it asap, please let me know if you
> > can post a patch promptly.
> 
> The userspace tool (pcitest [1]) that calls these IOCTLS prints "NOT
> OKAY" on 0 and "OKAY" for 1.
> 
> I'll change to negative value for error and still keep '0' for data
> mismatch error?

No, 0 as a return value from a system call means "success".  You can not
redefine it to mean something else for a tiny single kernel driver,
otherwise so much for consistency.

0 is success, -ERROR_NUMBER is an error, please read the ioctl man page.

thanks,

greg k-h