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Date:   Sun, 2 Dec 2018 07:30:34 -0500
From:   Konrad Rzeszutek Wilk <konrad@darnok.org>
To:     He Zhe <zhe.he@windriver.com>
Cc:     konrad.wilk@oracle.com, hch@lst.de, m.szyprowski@samsung.com,
        robin.murphy@arm.com, iommu@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kernel/dma: Fix panic caused by passing swiotlb to
 command line
Message-ID: <20181202123032.GA3166@localhost.localdomain>
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On Tue, Oct 30, 2018 at 07:06:10PM +0800, He Zhe wrote:
> 
> 
> On 2018/10/23 19:14, He Zhe wrote:
> >
> > On 2018/10/23 03:29, Konrad Rzeszutek Wilk wrote:
> >> On Sat, Sep 22, 2018 at 08:56:58PM +0800, He Zhe wrote:
> >>> May I have your input?
> >> Alternatively would it make more sense for it to assume some default
> >> value?
> > Maybe, but the original code has no default value and I have no idea
> > what default value is proper here.
> 
> Can anyone give some suggestions? Though I'd prefer to do nothing when
> no option is provided.

One provided the paramter for a reason. I would just do a small one, say
4MB.
> 
> Thanks,
> Zhe
> 
> >
> > Zhe
> >
> >>> Thanks,
> >>> Zhe
> >>>
> >>> On 2018年09月17日 11:27, zhe.he@windriver.com wrote:
> >>>> From: He Zhe <zhe.he@windriver.com>
> >>>>
> >>>> setup_io_tlb_npages does not check input argument before passing it
> >>>> to isdigit. The argument would be a NULL pointer if "swiotlb", without
> >>>> its value, is set in command line and thus causes the following panic.
> >>>>
> >>>> PANIC: early exception 0xe3 IP 10:ffffffffbb9b8e9f error 0 cr2 0x0
> >>>> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.0-rc3-yocto-standard+ #9
> >>>> [    0.000000] RIP: 0010:setup_io_tlb_npages+0xf/0x95
> >>>> ...
> >>>> [    0.000000] Call Trace:
> >>>> [    0.000000]  do_early_param+0x57/0x8e
> >>>> [    0.000000]  parse_args+0x208/0x320
> >>>> [    0.000000]  ? rdinit_setup+0x30/0x30
> >>>> [    0.000000]  parse_early_options+0x29/0x2d
> >>>> [    0.000000]  ? rdinit_setup+0x30/0x30
> >>>> [    0.000000]  parse_early_param+0x36/0x4d
> >>>> [    0.000000]  setup_arch+0x336/0x99e
> >>>> [    0.000000]  start_kernel+0x6f/0x4e6
> >>>> [    0.000000]  x86_64_start_reservations+0x24/0x26
> >>>> [    0.000000]  x86_64_start_kernel+0x6f/0x72
> >>>> [    0.000000]  secondary_startup_64+0xa4/0xb0
> >>>>
> >>>> This patch adds a check to prevent the panic.
> >>>>
> >>>> Signed-off-by: He Zhe <zhe.he@windriver.com>
> >>>> Cc: stable@vger.kernel.org
> >>>> Cc: konrad.wilk@oracle.com
> >>>> Cc: hch@lst.de
> >>>> Cc: m.szyprowski@samsung.com
> >>>> Cc: robin.murphy@arm.com
> >>>> ---
> >>>>  kernel/dma/swiotlb.c | 5 +++++
> >>>>  1 file changed, 5 insertions(+)
> >>>>
> >>>> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
> >>>> index 4f8a6db..46fc34e 100644
> >>>> --- a/kernel/dma/swiotlb.c
> >>>> +++ b/kernel/dma/swiotlb.c
> >>>> @@ -109,6 +109,11 @@ static int late_alloc;
> >>>>  static int __init
> >>>>  setup_io_tlb_npages(char *str)
> >>>>  {
> >>>> +	if (!str) {
> >>>> +		pr_err("Config string not provided\n");
> >>>> +		return -EINVAL;
> >>>> +	}
> >>>> +
> >>>>  	if (isdigit(*str)) {
> >>>>  		io_tlb_nslabs = simple_strtoul(str, &str, 0);
> >>>>  		/* avoid tail segment of size < IO_TLB_SEGSIZE */
> >>> _______________________________________________
> >>> iommu mailing list
> >>> iommu@lists.linux-foundation.org
> >>> https://lists.linuxfoundation.org/mailman/listinfo/iommu
> >
>