On 2023/3/22 17:01, David Hildenbrand wrote: > On 22.03.23 09:54, David Hildenbrand wrote: >> On 22.03.23 03:14, mawupeng wrote: >>> >>> >>> On 2023/3/21 22:19, David Hildenbrand wrote: >>>> On 21.03.23 08:44, mawupeng wrote: >>>>> >>>>> >>>>> On 2023/3/20 18:54, David Hildenbrand wrote: >>>>>> On 20.03.23 03:47, Wupeng Ma wrote: >>>>>>> From: Ma Wupeng <mawupeng1@xxxxxxxxxx> >>>>>>> >>>>>>> While testing mlock, we have a problem if the len of mlock is ULONG_MAX. >>>>>>> The return value of mlock is zero. But nothing will be locked since the >>>>>>> len in do_mlock overflows to zero due to the following code in mlock: >>>>>>> >>>>>>> len = PAGE_ALIGN(len + (offset_in_page(start))); >>>>>>> >>>>>>> The same problem happens in munlock. >>>>>>> >>>>>>> Add new check and return -EINVAL to fix this overflowing scenarios since >>>>>>> they are absolutely wrong. >>>>>> >>>>>> Thinking again, wouldn't we reject mlock(0, ULONG_MAX) now as well? >>>>> >>>>> mlock will return 0 if len is zero which is the same w/o this patchset. >>>>> Here is the calltrace if len is zero. >>>>> >>>>> mlock(len == 0) >>>>> do_mlock(len == 0) >>>>> if (!len) >>>>> return 0 >>>>> >>>> >>>> I was asking about addr=0, len=ULONG_MAX. >>>> >>>> IIUC, that used to work but could now fail? I haven't played with it, though. >>> >>> Thanks for reviewing. >>> >>> Previous for add = 0 and len == ULONG_MAX, mlock will return ok(0) since len overflows to zero. >>> IFAICT, this is not right since mlock do noting(lock nothing) and return ok(0). >>> >>> With this patch, for the same situation, mlock can return EINVAL as expected. >> >> Quoting the man page: >> >> "EINVAL (mlock(), mlock2(), and munlock()) The result of the addition >> addr+len was less than addr (e.g., the addition may have resulted in an >> overflow)." >> >> ULONG_MAX+0 = ULONG_MAX >> >> There is no overflow expected. The proper way to implement it would be >> to handle that case and not fail with EINVAL. >> >> At least that would be expected when reading the man page. >> > > As a side note, I agree that failing with EINVAL is better than doing noting (mlocking nothing). But I am not sure what we are expected to do in that case ... the man page is a bit vague on that. Thanks for you reviewing. Can we try to expand the man page since overflow is considered in man page? >
