From: Andrew Morton <akpm@linux-foundation.org>
To: Miaohe Lin <linmiaohe@huawei.com>
Cc: <imbrenda@linux.ibm.com>, <kirill.shutemov@linux.intel.com>,
<jack@suse.cz>, <jhubbard@nvidia.com>, <linux-mm@kvack.org>,
<linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 4/5] mm: gup: fix potential pgmap refcnt leak in __gup_device_huge()
Date: Sat, 7 Aug 2021 11:41:12 -0700 [thread overview]
Message-ID: <20210807114112.6e45b31c65dd62169fee8718@linux-foundation.org> (raw)
In-Reply-To: <20210807093620.21347-5-linmiaohe@huawei.com>
On Sat, 7 Aug 2021 17:36:19 +0800 Miaohe Lin <linmiaohe@huawei.com> wrote:
> When failed to try_grab_page, put_dev_pagemap() is missed. So pgmap
> refcnt will leak in this case. Also we remove the check for pgmap
> against NULL as it's also checked inside the put_dev_pagemap().
>
> ...
>
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -2253,14 +2253,14 @@ static int __gup_device_huge(unsigned long pfn, unsigned long addr,
> pages[*nr] = page;
> if (unlikely(!try_grab_page(page, flags))) {
> undo_dev_pagemap(nr, nr_start, flags, pages);
> + put_dev_pagemap(pgmap);
> return 0;
> }
> (*nr)++;
> pfn++;
> } while (addr += PAGE_SIZE, addr != end);
>
> - if (pgmap)
> - put_dev_pagemap(pgmap);
> + put_dev_pagemap(pgmap);
> return 1;
> }
We can simplify further, and remove the troublesome multiple return points?
--- a/mm/gup.c~mm-gup-fix-potential-pgmap-refcnt-leak-in-__gup_device_huge-fix
+++ a/mm/gup.c
@@ -2247,14 +2247,13 @@ static int __gup_device_huge(unsigned lo
pgmap = get_dev_pagemap(pfn, pgmap);
if (unlikely(!pgmap)) {
undo_dev_pagemap(nr, nr_start, flags, pages);
- return 0;
+ break;
}
SetPageReferenced(page);
pages[*nr] = page;
if (unlikely(!try_grab_page(page, flags))) {
undo_dev_pagemap(nr, nr_start, flags, pages);
- put_dev_pagemap(pgmap);
- return 0;
+ break;
}
(*nr)++;
pfn++;
_
next prev parent reply other threads:[~2021-08-07 18:41 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-07 9:36 [PATCH 0/5] Cleanups and fixup for gup Miaohe Lin
2021-08-07 9:36 ` [PATCH 1/5] mm: gup: remove set but unused local variable major Miaohe Lin
2021-08-09 9:21 ` David Hildenbrand
2021-08-07 9:36 ` [PATCH 2/5] mm: gup: remove unneed local variable orig_refs Miaohe Lin
2021-08-09 9:22 ` David Hildenbrand
2021-08-07 9:36 ` [PATCH 3/5] mm: gup: remove useless BUG_ON in __get_user_pages() Miaohe Lin
2021-08-09 9:23 ` David Hildenbrand
2021-08-07 9:36 ` [PATCH 4/5] mm: gup: fix potential pgmap refcnt leak in __gup_device_huge() Miaohe Lin
2021-08-07 18:41 ` Andrew Morton [this message]
2021-08-07 18:45 ` Andrew Morton
2021-08-08 21:16 ` John Hubbard
2021-08-07 9:36 ` [PATCH 5/5] mm: gup: use helper PAGE_ALIGNED in populate_vma_page_range() Miaohe Lin
2021-08-09 9:24 ` David Hildenbrand
2021-08-08 21:13 ` [PATCH 0/5] Cleanups and fixup for gup John Hubbard
2021-08-09 9:39 ` Claudio Imbrenda
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