Re: [PATCH v2] staging: erofs: keep corrupted fs from crashing kernel in erofs_namei()

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;

}