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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org,
        syzbot+dcb8b3587445007f5808@syzkaller.appspotmail.com,
        Andrew Price <anprice@redhat.com>,
        Bob Peterson <rpeterso@redhat.com>
Subject: [PATCH 4.4 08/86] gfs2: Dont leave s_fs_info pointing to freed memory in init_sbd
Date:   Thu, 29 Nov 2018 15:11:33 +0100
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4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Andrew Price <anprice@redhat.com>

commit 4c62bd9cea7bcf10292f7e4c57a2bca332942697 upstream.

When alloc_percpu() fails, sdp gets freed but sb->s_fs_info still points
to the same address. Move the assignment after that error check so that
s_fs_info can only point to a valid sdp or NULL, which is checked for
later in the error path, in gfs2_kill_super().

Reported-by: syzbot+dcb8b3587445007f5808@syzkaller.appspotmail.com
Signed-off-by: Andrew Price <anprice@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 fs/gfs2/ops_fstype.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/fs/gfs2/ops_fstype.c
+++ b/fs/gfs2/ops_fstype.c
@@ -71,13 +71,13 @@ static struct gfs2_sbd *init_sbd(struct
 	if (!sdp)
 		return NULL;
 
-	sb->s_fs_info = sdp;
 	sdp->sd_vfs = sb;
 	sdp->sd_lkstats = alloc_percpu(struct gfs2_pcpu_lkstats);
 	if (!sdp->sd_lkstats) {
 		kfree(sdp);
 		return NULL;
 	}
+	sb->s_fs_info = sdp;
 
 	set_bit(SDF_NOJOURNALID, &sdp->sd_flags);
 	gfs2_tune_init(&sdp->sd_tune);