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Date: Sun, 9 Dec 2018 07:52:56 +0100
From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Hou Tao <houtao1@huawei.com>
Cc: <linux-mtd@lists.infradead.org>, <dwmw2@infradead.org>,
 <linux-kernel@vger.kernel.org>, <richard.weinberger@gmail.com>
Subject: Re: [PATCH] jffs2: fix invocations of dbg_xattr() for dead
 jffs2_xattr_ref
Message-ID: <20181209075256.43ca759f@bbrezillon>
In-Reply-To: <20181020110753.98407-1-houtao1@huawei.com>
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On Sat, 20 Oct 2018 19:07:53 +0800
Hou Tao <houtao1@huawei.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@huawei.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).

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);