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Date:   Sat, 27 Aug 2022 17:36:53 -0700
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Subject: Re: [PATCH] mm/gup.c: Fix uninitialized return value on
 __gup_longterm_locked()
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To:     Shigeru Yoshida <syoshida@redhat.com>, akpm@linux-foundation.org
Cc:     apopple@nvidia.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, Shigeru Yoshida <yshigeru@gmail.com>,
        Dan Carpenter <dan.carpenter@oracle.com>
References: <20220827230037.78876-1-syoshida@redhat.com>
From:   John Hubbard <jhubbard@nvidia.com>
In-Reply-To: <20220827230037.78876-1-syoshida@redhat.com>
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On 8/27/22 16:00, Shigeru Yoshida wrote:
> From: Shigeru Yoshida <yshigeru@gmail.com>
> 
> In __gup_longterm_locked(), it returns uninitialized value if
> __get_user_pages_locked() fails on the first iteration of the loop
> since rc is not initialized.
> 
> This patch fixes this issue by properly returning error code if
> __get_user_pages_locked() fails.
> 
> Fixes: 11147539df44 (mm/gup.c: Fix return value for __gup_longterm_locked())
> Cc: Alistair Popple <apopple@nvidia.com>
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Shigeru Yoshida <yshigeru@gmail.com>
> ---
>  mm/gup.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/gup.c b/mm/gup.c
> index ad59c796d4d3..66d8619e02ad 100644
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2110,8 +2110,10 @@ static long __gup_longterm_locked(struct mm_struct *mm,
>  		nr_pinned_pages = __get_user_pages_locked(mm, start, nr_pages,
>  							  pages, vmas, NULL,
>  							  gup_flags);
> -		if (nr_pinned_pages <= 0)
> +		if (nr_pinned_pages <= 0) {
> +			rc = nr_pinned_pages;
>  			break;
> +		}
>  		rc = check_and_migrate_movable_pages(nr_pinned_pages, pages);
>  	} while (rc == -EAGAIN);
>  	memalloc_pin_restore(flags);

Sorry I didn't catch the 0th loop iteration problem on the 
first review of this. Anyway,

Reviewed-by: John Hubbard <jhubbard@nvidia.com>


thanks,

-- 
John Hubbard
NVIDIA