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SubjectRe: [PATCH v2] staging: erofs: keep corrupted fs from crashing kernel in erofs_namei()
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Hi Chao,

On 2019/2/18 9:39, Chao Yu wrote:
> If the image is corrupted, qn->name[i] may be anything, as you commented
> above DBG_BUGON(), we really don't need to go through any later codes, it
> can avoid potentially encoutnering wrong condition.
>
> * otherwise, it will return 1 to just skip the invalid name
>

Just I commented in the following source code, qn is actually the user requested
name allocated in __d_alloc, which can be guaranteed with the trailing '\0' and
it is a valid string.

Thanks,
Gao Xiang

>>>> +
>>>> + /* qd could not have trailing '\0' */
>>>> + /* However it is absolutely safe if < qd->end */
>>>> + while (qd->name + i < qd->end && qd->name[i] != '\0') {
>>>> + if (qn->name[i] != qd->name[i]) {
>>>> + *matched = i;
>>>> + return qn->name[i] > qd->name[i] ? 1 : -1;
>>>> }
>>>> - return (qn->len > qd->len);
>>>> + ++i;
>>>> }
>>>> -
>>>> - if (qn->name[i] != qd->name[i]) {
>>>> - *matched = i;
>>>> - return qn->name[i] > qd->name[i] ? 1 : -1;
>>>> - }
>>>> -
>>>> - ++i;
>>>> - goto loop;
>>>> + *matched = i;
>>>> + /* See comments in __d_alloc on the terminating NUL character */
>>>> + return qn->name[i] == '\0' ? 0 : 1;
>>>> }

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