Messages in this thread | | | Subject | Re: [PATCH] block: Fix minor range check in device_add_disk() | From | Yu Kuai <> | Date | Mon, 30 Oct 2023 17:26:51 +0800 |
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Hi,
在 2023/10/26 16:52, zhongjinghua 写道: > > 在 2023/10/25 18:06, Tetsuo Handa 写道: >> On 2023/10/25 17:46, Zhong Jinghua wrote: >>> Checks added in patch: >>> commit e338924bd05d ("block: check minor range in device_add_disk()") >>> ignore the problem of first_minore < 0 and disk->minors < 0. >> What is the problem of first_minor < 0 or disk->minors < 0 ? >> Are negative values legal/illegal ? > > These two values are used as the secondary device number and the maximum > number of partitions, which is illegal if negative. Then first_minore > and disk->minors are signed numbers, and the sum may be less than > MINORMASK to bypass the check.
Let me complement it, first_minor and minors can be set by driver, and driver allow set them throuhh ioctl/sysfs from user parameters, for example:
If user pass in -1, and each disk support 8 partitions, driver will usually set:
disk->first_minor = -1 * 8 = -8; disk->minors = 8;
Then first_minor + minors = 0, then the following condition can't detect this case:
if (disk->first_minor + disk->minors > MINORMASK + 1)
By the way, we never limit how first_minor and minors is set by driver, and it's illegal if driver set first_minor = -4, and minors = 8.
Thanks, Kuai
> > . >
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