Messages in this thread | | | Date | Mon, 6 Feb 2023 18:05:01 +0100 | Subject | Re: [PATCH v3 1/4] mm/mlock: return EINVAL if len overflows for mlock/munlock | From | David Hildenbrand <> |
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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@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. >>> >>> Return 0 early to avoid burn a bunch of cpu cycles if len == 0. >>> >>> Signed-off-by: Ma Wupeng <mawupeng1@huawei.com> >>> --- >>> 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?
-- Thanks,
David / dhildenb
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