Re: [PATCH 0/1] Fix NULL pointer dereference in register_disk

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On 2/20/19 6:27 AM, zhengbin wrote:
> When I use syzkaller test kernel, there is a NULL pointer dereference
> in register_disk. The better solution is add return code to
> __device_add_disk. There is a patchset(http://lists.infradead.org/pipermail
> /linux-nvme/2016-August/005860.html) from Fam Zheng, int this patchset, the
> modify is as follows:
>  int device_add_disk() {
>         ...alloc A...
>         retval = alloc B
>         if (retval)
>             goto fail;
>         ...
> 	fail:
> 	    return retval;  --->did not free A
>    }
> There are many callers, ie:
> loop_add-->add_disk-->device_add_disk-->__device_add_disk
> loop_remove-->del_gendisk
> ----->This will free all resources, inclue B(free fail)
> 
> Maybe the better way is that if device_add_disk return fail, it should
> free all resources? This needs to modify all the callers(Otherwise the
> callers will double free), unfortunately, I am not very familiar with it.

That can/should be done when we actually deal with error handling properly
in this path. I have applied your patch.

-- 
Jens Axboe




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