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Message-ID: <753c53d3-84a6-da73-4121-0db4a71e4fde@redhat.com>
Date: Fri, 3 Feb 2023 18:14:29 +0100
From: David Hildenbrand <david@...hat.com>
To: Wupeng Ma <mawupeng1@...wei.com>, akpm@...ux-foundation.org
Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org,
kuleshovmail@...il.com, aneesh.kumar@...ux.ibm.com
Subject: Re: [PATCH v3 1/4] mm/mlock: return EINVAL if len overflows for
mlock/munlock
On 28.01.23 07:32, Wupeng Ma wrote:
> From: Ma Wupeng <mawupeng1@...wei.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@...wei.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?
--
Thanks,
David / dhildenb
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