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?
Thanks for reviewing.
I will test this and resend & reply this.
>
>>
>> Signed-off-by: Ma Wupeng <mawupeng1@xxxxxxxxxx>
>> ---
>> mm/mlock.c | 8 ++++++++
>> 1 file changed, 8 insertions(+)
>>
>> diff --git a/mm/mlock.c b/mm/mlock.c
>> index 617469fce96d..eb68476da497 100644
>> --- a/mm/mlock.c
>> +++ b/mm/mlock.c
>> @@ -568,6 +568,7 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
>> unsigned long locked;
>> unsigned long lock_limit;
>> int error = -ENOMEM;
>> + size_t old_len = len;
>> start = untagged_addr(start);
>> @@ -577,6 +578,9 @@ static __must_check int do_mlock(unsigned long start, size_t len, vm_flags_t fla
>> len = PAGE_ALIGN(len + (offset_in_page(start)));
>> start &= PAGE_MASK;
>> + if (old_len != 0 && len == 0)
>
> if (old_len && !len)
>
>> + return -EINVAL;
>> +
>> lock_limit = rlimit(RLIMIT_MEMLOCK);
>> lock_limit >>= PAGE_SHIFT;
>> locked = len >> PAGE_SHIFT;
>> @@ -631,12 +635,16 @@ SYSCALL_DEFINE3(mlock2, unsigned long, start, size_t, len, int, flags)
>> SYSCALL_DEFINE2(munlock, unsigned long, start, size_t, len)
>> {
>> int ret;
>> + size_t old_len = len;
>> start = untagged_addr(start);
>> len = PAGE_ALIGN(len + (offset_in_page(start)));
>> start &= PAGE_MASK;
>> + if (old_len != 0 && len == 0)
>
> if (old_len && !len)
Sorry for wasting your time.
I send the wrong version of this patchset, this is the older version.
>
>> + return -EINVAL;
>> +
>> if (mmap_write_lock_killable(current->mm))
>> return -EINTR;
>> ret = apply_vma_lock_flags(start, len, 0);
>
