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Groups > linux.kernel > #1673353 > unrolled thread

Re: [PATCH] f2fs: fix ref of discard command

Started byChao Yu <yuchao0@huawei.com>
First post2017-06-23 10:20 +0200
Last post2017-06-24 18:30 +0200
Articles 2 — 2 participants

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  Re: [PATCH] f2fs: fix ref of discard command Chao Yu <yuchao0@huawei.com> - 2017-06-23 10:20 +0200
    Re: [PATCH] f2fs: fix ref of discard command Jaegeuk Kim <jaegeuk@kernel.org> - 2017-06-24 18:30 +0200

#1673353 — Re: [PATCH] f2fs: fix ref of discard command

FromChao Yu <yuchao0@huawei.com>
Date2017-06-23 10:20 +0200
SubjectRe: [PATCH] f2fs: fix ref of discard command
Message-ID<tVrYS-8aL-19@gated-at.bofh.it>
Hi Jaegeuk,

On 2017/6/12 11:04, Jaegeuk Kim wrote:
> This patch resolves kernel panic for xfstests/081, caused by recent f2fs_bug_on
> 
>   f2fs: add f2fs_bug_on in __remove_discard_cmd
> 
> Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> ---
>  fs/f2fs/segment.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 86a0c1095939..a6d77388a806 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -1025,6 +1025,8 @@ static void __wait_discard_cmd(struct f2fs_sb_info *sbi, bool wait_cond)
>  	list_for_each_entry_safe(dc, tmp, wait_list, list) {
>  		if (!wait_cond || (dc->state == D_DONE && !dc->ref)) {
>  			wait_for_completion_io(&dc->wait);
> +			if (dc->state == D_DONE && dc->ref)
> +				dc->ref--;

How about using ("f2fs: stop discard thread in prior during umount") instead of
this one? As dereference of dc here will lead use-after-free of real referrer.

Thanks,

>  			__remove_discard_cmd(sbi, dc);
>  		} else {
>  			dc->ref++;
> 

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#1674106

FromJaegeuk Kim <jaegeuk@kernel.org>
Date2017-06-24 18:30 +0200
Message-ID<tVW6C-1BX-13@gated-at.bofh.it>
In reply to#1673353
On 06/23, Chao Yu wrote:
> Hi Jaegeuk,
> 
> On 2017/6/12 11:04, Jaegeuk Kim wrote:
> > This patch resolves kernel panic for xfstests/081, caused by recent f2fs_bug_on
> > 
> >   f2fs: add f2fs_bug_on in __remove_discard_cmd
> > 
> > Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
> > ---
> >  fs/f2fs/segment.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> > index 86a0c1095939..a6d77388a806 100644
> > --- a/fs/f2fs/segment.c
> > +++ b/fs/f2fs/segment.c
> > @@ -1025,6 +1025,8 @@ static void __wait_discard_cmd(struct f2fs_sb_info *sbi, bool wait_cond)
> >  	list_for_each_entry_safe(dc, tmp, wait_list, list) {
> >  		if (!wait_cond || (dc->state == D_DONE && !dc->ref)) {
> >  			wait_for_completion_io(&dc->wait);
> > +			if (dc->state == D_DONE && dc->ref)
> > +				dc->ref--;
> 
> How about using ("f2fs: stop discard thread in prior during umount") instead of
> this one? As dereference of dc here will lead use-after-free of real referrer.

Yup, I'll also verify that.
Thank you. :)

> 
> Thanks,
> 
> >  			__remove_discard_cmd(sbi, dc);
> >  		} else {
> >  			dc->ref++;
> > 

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