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

[He Zhe]

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.

Zhe

>> Thanks,
>> Zhe
>>
>> On 2018å09æ17æ 11:27, zhe.he@xxxxxxxxxxxxx wrote:
>>> From: He Zhe <zhe.he@xxxxxxxxxxxxx>
>>>
>>> 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@xxxxxxxxxxxxx>
>>> Cc: stable@xxxxxxxxxxxxxxx
>>> Cc: konrad.wilk@xxxxxxxxxx
>>> Cc: hch@xxxxxx
>>> Cc: m.szyprowski@xxxxxxxxxxx
>>> Cc: robin.murphy@xxxxxxx
>>> ---
>>>  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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