gfs2: Fix NULL pointer dereference in gfs2_rgrp_dump

When an rindex entry is found to be corrupt, compute_bitstructs() calls
gfs2_consist_rgrpd() which calls gfs2_rgrp_dump() like this:

    gfs2_rgrp_dump(NULL, rgd->rd_gl, fs_id_buf);

gfs2_rgrp_dump then dereferences the gl without checking it and we get

    BUG: KASAN: null-ptr-deref in gfs2_rgrp_dump+0x28/0x280

because there's no rgrp glock involved while reading the rindex on mount.

Fix this by changing gfs2_rgrp_dump to take an rgrp argument.

Reported-by: syzbot+43fa87986bdd31df9de6@syzkaller.appspotmail.com
Signed-off-by: Andrew Price <anprice@redhat.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

fs/gfs2/glops.c

@@ -227,6 +227,15 @@ static void rgrp_go_inval(struct gfs2_glock *gl, int flags)
 		rgd->rd_flags &= ~GFS2_RDF_UPTODATE;
 }
 
+static void gfs2_rgrp_go_dump(struct seq_file *seq, struct gfs2_glock *gl,
+			      const char *fs_id_buf)
+{
+	struct gfs2_rgrpd *rgd = gfs2_glock2rgrp(gl);
+
+	if (rgd)
+		gfs2_rgrp_dump(seq, rgd, fs_id_buf);
+}
+
 static struct gfs2_inode *gfs2_glock2inode(struct gfs2_glock *gl)
 {
 	struct gfs2_inode *ip;
@@ -712,7 +721,7 @@ const struct gfs2_glock_operations gfs2_rgrp_glops = {
 	.go_sync = rgrp_go_sync,
 	.go_inval = rgrp_go_inval,
 	.go_lock = gfs2_rgrp_go_lock,
-	.go_dump = gfs2_rgrp_dump,
+	.go_dump = gfs2_rgrp_go_dump,
 	.go_type = LM_TYPE_RGRP,
 	.go_flags = GLOF_LVB,
 };

fs/gfs2/rgrp.c

@@ -2209,20 +2209,17 @@ static void rgblk_free(struct gfs2_sbd *sdp, struct gfs2_rgrpd *rgd,
 /**
  * gfs2_rgrp_dump - print out an rgrp
  * @seq: The iterator
- * @gl: The glock in question
+ * @rgd: The rgrp in question
  * @fs_id_buf: pointer to file system id (if requested)
  *
  */
 
-void gfs2_rgrp_dump(struct seq_file *seq, struct gfs2_glock *gl,
+void gfs2_rgrp_dump(struct seq_file *seq, struct gfs2_rgrpd *rgd,
 		    const char *fs_id_buf)
 {
-	struct gfs2_rgrpd *rgd = gl->gl_object;
 	struct gfs2_blkreserv *trs;
 	const struct rb_node *n;
 
-	if (rgd == NULL)
-		return;
 	gfs2_print_dbg(seq, "%s R: n:%llu f:%02x b:%u/%u i:%u r:%u e:%u\n",
 		       fs_id_buf,
 		       (unsigned long long)rgd->rd_addr, rgd->rd_flags,
@@ -2253,7 +2250,7 @@ static void gfs2_rgrp_error(struct gfs2_rgrpd *rgd)
 		(unsigned long long)rgd->rd_addr);
 	fs_warn(sdp, "umount on all nodes and run fsck.gfs2 to fix the error\n");
 	sprintf(fs_id_buf, "fsid=%s: ", sdp->sd_fsname);
-	gfs2_rgrp_dump(NULL, rgd->rd_gl, fs_id_buf);
+	gfs2_rgrp_dump(NULL, rgd, fs_id_buf);
 	rgd->rd_flags |= GFS2_RDF_ERROR;
 }
 

fs/gfs2/rgrp.h

@@ -67,7 +67,7 @@ extern void gfs2_rlist_add(struct gfs2_inode *ip, struct gfs2_rgrp_list *rlist,
 extern void gfs2_rlist_alloc(struct gfs2_rgrp_list *rlist);
 extern void gfs2_rlist_free(struct gfs2_rgrp_list *rlist);
 extern u64 gfs2_ri_total(struct gfs2_sbd *sdp);
-extern void gfs2_rgrp_dump(struct seq_file *seq, struct gfs2_glock *gl,
+extern void gfs2_rgrp_dump(struct seq_file *seq, struct gfs2_rgrpd *rgd,
 			   const char *fs_id_buf);
 extern int gfs2_rgrp_send_discards(struct gfs2_sbd *sdp, u64 offset,
 				   struct buffer_head *bh,

fs/gfs2/util.c

@@ -419,7 +419,7 @@ void gfs2_consist_rgrpd_i(struct gfs2_rgrpd *rgd,
 	char fs_id_buf[sizeof(sdp->sd_fsname) + 7];
 
 	sprintf(fs_id_buf, "fsid=%s: ", sdp->sd_fsname);
-	gfs2_rgrp_dump(NULL, rgd->rd_gl, fs_id_buf);
+	gfs2_rgrp_dump(NULL, rgd, fs_id_buf);
 	gfs2_lm(sdp,
 		"fatal: filesystem consistency error\n"
 		"  RG = %llu\n"