linux-kernel - Re: [PATCH] jffs2: fix invocations of dbg_xattr() for dead jffs2_xattr

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Date:   Sat, 15 Dec 2018 21:17:09 +0800
From:   Hou Tao <houtao1@...wei.com>
To:     Richard Weinberger <richard.weinberger@...il.com>,
        <boris.brezillon@...tlin.com>
CC:     <linux-mtd@...ts.infradead.org>,
        David Woodhouse <dwmw2@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] jffs2: fix invocations of dbg_xattr() for dead
 jffs2_xattr_ref



On 2018/12/14 5:53, Richard Weinberger wrote:
> On Sun, Dec 9, 2018 at 7:52 AM Boris Brezillon
> <boris.brezillon@...tlin.com> wrote:
>>
>> On Sat, 20 Oct 2018 19:07:53 +0800
>> Hou Tao <houtao1@...wei.com> wrote:
>>
>>> When jffs2_xattr_ref is dead, xref->ic or xref->xd will be invalid
>>> because these fields will be reused as xref->ino or xref->xid,
>>> so access xref->ic->ino or xref->xd->xid will lead to Oops.
>>>
>>> Fix the problem by checking whether or not it is a dead xref.
>>>
>>> Signed-off-by: Hou Tao <houtao1@...wei.com>
>>> ---
>>>  fs/jffs2/xattr.c | 9 +++++++--
>>>  1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/fs/jffs2/xattr.c b/fs/jffs2/xattr.c
>>> index 3d40fe02b003..0c4c7891556d 100644
>>> --- a/fs/jffs2/xattr.c
>>> +++ b/fs/jffs2/xattr.c
>>> @@ -550,7 +550,8 @@ static int save_xattr_ref(struct jffs2_sb_info *c, struct jffs2_xattr_ref *ref)
>>>       ref->xseqno = xseqno;
>>>       jffs2_add_physical_node_ref(c, phys_ofs | REF_PRISTINE, PAD(sizeof(rr)), (void *)ref);
>>>
>>> -     dbg_xattr("success on saving xref (ino=%u, xid=%u)\n", ref->ic->ino, ref->xd->xid);
>>> +     dbg_xattr("success on saving xref (ino=%u, xid=%u)\n",
>>> +                     je32_to_cpu(rr.ino), je32_to_cpu(rr.xid));
>>
>> Nit: align the second line on the open parens (same applies to the
>> other chunk).

Thanks for pointing it out, I will fix them.

>> Sorry, I can't comment on the actual change. I'll let Richard look
>> at it.
>>
>>>
>>>       return 0;
>>>  }
>>> @@ -1329,7 +1330,11 @@ int jffs2_garbage_collect_xattr_ref(struct jffs2_sb_info *c, struct jffs2_xattr_
>>>       rc = save_xattr_ref(c, ref);
>>>       if (!rc)
>>>               dbg_xattr("xref (ino=%u, xid=%u) GC'ed from %#08x to %08x\n",
>>> -                       ref->ic->ino, ref->xd->xid, old_ofs, ref_offset(ref->node));
>>> +                             is_xattr_ref_dead(ref) ?
>>> +                                     ref->ino : ref->ic->ino,
>>> +                             is_xattr_ref_dead(ref) ?
>>> +                                     ref->xid : ref->xd->xid,
>>> +                             old_ofs, ref_offset(ref->node));
>>>   out:
>>>       if (!rc)
>>>               jffs2_mark_node_obsolete(c, raw);
>>
> 
> Since is_xattr_ref_dead() is cheap, can you please add two macros.
> Something like:
> static inline uint32_t xattr_ref_ino(struct jffs2_xattr_ref *ref) {
>  if (is_xattr_ref_dead(ref))
>   return ref>ino;
>  else
>   return ref->ic->ino;
> }
> 
> Same for xid.
> 
Yes, there would be better, will do that.

Thanks,
Tao