From mboxrd@z Thu Jan 1 00:00:00 1970 From: Bob Peterson Date: Thu, 1 Oct 2015 13:00:42 -0400 (EDT) Subject: [Cluster-devel] [GFS2 PATCH] gfs2: Add missing else in trans_add_meta/data In-Reply-To: <1226969049.38347148.1443718728281.JavaMail.zimbra@redhat.com> Message-ID: <1180070116.38350756.1443718842083.JavaMail.zimbra@redhat.com> List-Id: To: cluster-devel.redhat.com MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Hi, This patch fixes a timing window that causes a segfault. The problem is that bd can remain NULL throughout the function and then reference that NULL pointer if the bh->b_private starts out NULL, then someone sets it to non-NULL inside the locking. In that case, bd still needs to be set. Regards, Bob Peterson Red Hat File Systems Signed-off-by: Bob Peterson --- fs/gfs2/trans.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/fs/gfs2/trans.c b/fs/gfs2/trans.c index b95d0d6..0c1bde3 100644 --- a/fs/gfs2/trans.c +++ b/fs/gfs2/trans.c @@ -176,6 +176,8 @@ void gfs2_trans_add_data(struct gfs2_glock *gl, struct buffer_head *bh) unlock_buffer(bh); if (bh->b_private == NULL) bd = gfs2_alloc_bufdata(gl, bh, &gfs2_databuf_lops); + else + bd = bh->b_private; lock_buffer(bh); gfs2_log_lock(sdp); } @@ -236,6 +238,8 @@ void gfs2_trans_add_meta(struct gfs2_glock *gl, struct buffer_head *bh) lock_page(bh->b_page); if (bh->b_private == NULL) bd = gfs2_alloc_bufdata(gl, bh, &gfs2_buf_lops); + else + bd = bh->b_private; unlock_page(bh->b_page); lock_buffer(bh); gfs2_log_lock(sdp);