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SubjectRe: [PATCH] nilfs2: fix potential use after free
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Hi, Pan Bian

Thank you for feeding back this patch.
I reviewed this and am thinking this must be sent to upstream.

Did you see any kernel oops on this bug ?

Regards,
Ryusuke Konishi

On Mon, 26 Nov 2018 11:08:29 +0800, Pan Bian <bianpan2016@163.com> wrote:
> brelse(bh) is called to drop the reference count of bh when the call
> to nilfs_dat_translate fails. If the reference count hits 0, bh may be
> freed. However, bh->b_page is unlocked and put after that, which may
> result in a use-after-free bug. This patch moves the release operation
> after unlocking and putting the page.
>
> Signed-off-by: Pan Bian <bianpan2016@163.com>
> ---
> fs/nilfs2/gcinode.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/fs/nilfs2/gcinode.c b/fs/nilfs2/gcinode.c
> index aa3c328..a24bb29 100644
> --- a/fs/nilfs2/gcinode.c
> +++ b/fs/nilfs2/gcinode.c
> @@ -73,10 +73,8 @@ int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff,
> struct the_nilfs *nilfs = inode->i_sb->s_fs_info;
>
> err = nilfs_dat_translate(nilfs->ns_dat, vbn, &pbn);
> - if (unlikely(err)) { /* -EIO, -ENOMEM, -ENOENT */
> - brelse(bh);
> + if (unlikely(err)) /* -EIO, -ENOMEM, -ENOENT */
> goto failed;
> - }
> }
>
> lock_buffer(bh);
> @@ -102,6 +100,8 @@ int nilfs_gccache_submit_read_data(struct inode *inode, sector_t blkoff,
> failed:
> unlock_page(bh->b_page);
> put_page(bh->b_page);
> + if (unlikely(err))
> + brelse(bh);
> return err;
> }
>
> --
> 2.7.4
>
>

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