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

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Message-Id: <20180918092834eucas1p1ebdbc3051a7ca8bbacec26b955689784~VdHnT_5yZ0331203312eucas1p1U@eucas1p1.samsung.com>
Date:   Tue, 18 Sep 2018 11:28:33 +0200
From:   Marek Szyprowski <m.szyprowski@...sung.com>
To:     zhe.he@...driver.com, hch@....de, robin.murphy@....com,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] kernel/dma: Fix panic caused by passing cma to command
 line

Hi

On 2018-09-17 05:24, zhe.he@...driver.com wrote:
> From: He Zhe <zhe.he@...driver.com>
>
> early_cma does not check input argument before passing it to
> simple_strtoull. The argument would be a NULL pointer if "cma", without
> its value, is set in command line and thus causes the following panic.
>
> PANIC: early exception 0xe3 IP 10:ffffffffa3e9db8d error 0 cr2 0x0
> [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.19.0-rc3-yocto-standard+ #7
> [    0.000000] RIP: 0010:_parse_integer_fixup_radix+0xd/0x70
> ...
> [    0.000000] Call Trace:
> [    0.000000]  simple_strtoull+0x29/0x70
> [    0.000000]  memparse+0x26/0x90
> [    0.000000]  early_cma+0x17/0x6a
> [    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@...driver.com>
> Cc: stable@...r.kernel.org
> Cc: hch@....de
> Cc: m.szyprowski@...sung.com
> Cc: robin.murphy@....com

Thanks for the fix.

Reviewed-by: Marek Szyprowski <m.szyprowski@...sung.com>

> ---
>   kernel/dma/contiguous.c | 6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c
> index 286d823..b2a8790 100644
> --- a/kernel/dma/contiguous.c
> +++ b/kernel/dma/contiguous.c
> @@ -49,7 +49,11 @@ static phys_addr_t limit_cmdline;
>   
>   static int __init early_cma(char *p)
>   {
> -	pr_debug("%s(%s)\n", __func__, p);
> +	if (!p) {
> +		pr_err("Config string not provided\n");
> +		return -EINVAL;
> +	}
> +
>   	size_cmdline = memparse(p, &p);
>   	if (*p != '@')
>   		return 0;

Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland