Re: [PATCH] kernel/dma: Fix panic caused by passing swiotlb to command line

[He Zhe <zhe.he@windriver.com>]

On 2018/12/2 20:30, Konrad Rzeszutek Wilk wrote:
> 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.

OK. Thanks, I'll send v2.

Zhe

>> 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 */
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