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

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

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.

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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