On 2023/2/7 1:05, David Hildenbrand wrote: > On 06.02.23 01:48, mawupeng wrote: >> >> >> On 2023/2/4 1:14, David Hildenbrand wrote: >>> On 28.01.23 07:32, 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. >>>> >>>> Return 0 early to avoid burn a bunch of cpu cycles if len == 0. >>>> >>>> Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx> >>>> --- >>>> mm/mlock.c | 14 ++++++++++++-- >>>> 1 file changed, 12 insertions(+), 2 deletions(-) >>>> >>>> diff --git a/mm/mlock.c b/mm/mlock.c >>>> index 7032f6dd0ce1..eb09968ba27f 100644 >>>> --- a/mm/mlock.c >>>> +++ b/mm/mlock.c >>>> @@ -478,8 +478,6 @@ static int apply_vma_lock_flags(unsigned long start, size_t len, >>>> end = start + len; >>>> if (end < start) >>>> return -EINVAL; >>>> - if (end == start) >>>> - return 0; >>>> vma = mas_walk(&mas); >>>> if (!vma) >>>> return -ENOMEM; >>>> @@ -575,7 +573,13 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla >>>> if (!can_do_mlock()) >>>> return -EPERM; >>>> + if (!len) >>>> + return 0; >>>> + >>>> len = PAGE_ALIGN(len + (offset_in_page(start))); >>>> + if (!len) >>>> + return -EINVAL; >>>> + >>>> start &= PAGE_MASK; >>> >>> The "ordinary" overflows are detected in apply_vma_lock_flags(), correct? >> >> Overflow is not checked anywhere however the ordinary return early if len == 0 is detected in apply_vma_lock_flags(). >> > > I meant the > > end = start + len; > if (end < start) > return -EINVAL; > > Essentially, what I wanted to double-check is that with your changes, we catch all kinds of overflows as documented in the man page, correct? Oh i see. You are right, The "ordinary" overflows are detected for mlock/munlock in apply_vma_lock_flags(). Yes, we may need to update the man page for all these four syscalls. Thanks, mawupeng. >
