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Subject: Re: [PATCH] kernel/dma: Fix panic caused by passing swiotlb to
 command line
To:     <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>
References: <1537154831-447363-1-git-send-email-zhe.he@windriver.com>
From:   He Zhe <zhe.he@windriver.com>
Message-ID: <c3536f4f-9bde-4f7f-a180-aa569d4e786d@windriver.com>
Date:   Sat, 22 Sep 2018 20:56:58 +0800
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May I have your input?

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 */