Messages in this thread Patch in this message | | | Date | Mon, 20 Mar 2023 11:54:11 +0100 | From | David Hildenbrand <> | Subject | Re: [PATCH v4 1/4] mm/mlock: return EINVAL if len overflows for mlock/munlock |
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On 20.03.23 03:47, Wupeng Ma wrote: > From: Ma Wupeng <mawupeng1@huawei.com> > > 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?
> > Signed-off-by: Ma Wupeng <mawupeng1@huawei.com> > --- > 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)
> + return -EINVAL; > + > if (mmap_write_lock_killable(current->mm)) > return -EINTR; > ret = apply_vma_lock_flags(start, len, 0);
-- Thanks,
David / dhildenb
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