gfs2: assign rgrp glock before compute_bitstructs

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>

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index 0fb3c01bc55773b73ab1da616f8f6544c1b06366..9b04a570c58263707ac99d19eb55bc480389cd3c 100644 (file)
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -922,15 +922,15 @@ static int read_rindex_entry(struct gfs2_inode *ip)
        spin_lock_init(&rgd->rd_rsspin);
        mutex_init(&rgd->rd_mutex);
 
-       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_PREFERRED;
        if (rgd->rd_data > sdp->sd_max_rg_data)
@@ -944,6 +944,7 @@ static int read_rindex_entry(struct gfs2_inode *ip)
        }
 
        error = 0; /* someone else read in the rgrp; free it and ignore it */
+fail_glock:
        gfs2_glock_put(rgd->rd_gl);
 
 fail: