[PATCH 4.9 03/24] gfs2: assign rgrp glock before compute_bitstructs

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Bob Peterson <rpeterso@redhat.com>

commit 428f651cb80b227af47fc302e4931791f2fb4741 upstream.

Before this patch, function read_rindex_entry called compute_bitstructs
before it allocated a glock for the rgrp. But if compute_bitstructs found
a problem with the rgrp, it called gfs2_consist_rgrpd, and that called
gfs2_dump_glock for rgd->rd_gl which had not yet been assigned.

read_rindex_entry
   compute_bitstructs
      gfs2_consist_rgrpd
         gfs2_dump_glock <---------rgd->rd_gl was not set.

This patch changes read_rindex_entry so it assigns an rgrp glock before
calling compute_bitstructs so gfs2_dump_glock does not reference an
unassigned pointer. If an error is discovered, the glock must also be
put, so a new goto and label were added.

Reported-by: syzbot+c6fd14145e2f62ca0784@syzkaller.appspotmail.com
Signed-off-by: Bob Peterson <rpeterso@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 fs/gfs2/rgrp.c |    9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -917,15 +917,15 @@ static int read_rindex_entry(struct gfs2
 	rgd->rd_bitbytes = be32_to_cpu(buf.ri_bitbytes);
 	spin_lock_init(&rgd->rd_rsspin);
 
-	error = compute_bitstructs(rgd);
-	if (error)
-		goto fail;
-
 	error = gfs2_glock_get(sdp, rgd->rd_addr,
 			       &gfs2_rgrp_glops, CREATE, &rgd->rd_gl);
 	if (error)
 		goto fail;
 
+	error = compute_bitstructs(rgd);
+	if (error)
+		goto fail_glock;
+
 	rgd->rd_rgl = (struct gfs2_rgrp_lvb *)rgd->rd_gl->gl_lksb.sb_lvbptr;
 	rgd->rd_flags &= ~(GFS2_RDF_UPTODATE | GFS2_RDF_PREFERRED);
 	if (rgd->rd_data > sdp->sd_max_rg_data)
@@ -942,6 +942,7 @@ static int read_rindex_entry(struct gfs2
 	}
 
 	error = 0; /* someone else read in the rgrp; free it and ignore it */
+fail_glock:
 	gfs2_glock_put(rgd->rd_gl);
 
 fail: