LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
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++;
_


  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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20210807114112.6e45b31c65dd62169fee8718@linux-foundation.org \
    --to=akpm@linux-foundation.org \
    --cc=imbrenda@linux.ibm.com \
    --cc=jack@suse.cz \
    --cc=jhubbard@nvidia.com \
    --cc=kirill.shutemov@linux.intel.com \
    --cc=linmiaohe@huawei.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --subject='Re: [PATCH 4/5] mm: gup: fix potential pgmap refcnt leak in __gup_device_huge()' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).