gfs2: Fix kernel NULL pointer dereference in gfs2_rgrp_dump

Syzkaller has reported a NULL pointer dereference when accessing
rgd->rd_rgl in gfs2_rgrp_dump().  This can happen when creating
rgd->rd_gl fails in read_rindex_entry().  Add a NULL pointer check in
gfs2_rgrp_dump() to prevent that.

Reported-and-tested-by: syzbot+da0fc229cc1ff4bb2e6d@syzkaller.appspotmail.com
Link: https://syzkaller.appspot.com/bug?extid=da0fc229cc1ff4bb2e6d
Fixes: 72244b6bc752 ("gfs2: improve debug information when lvb mismatches are found")
Signed-off-by: Osama Muhammad <osmtendev@gmail.com>
Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>

diff --git a/fs/gfs2/rgrp.c b/fs/gfs2/rgrp.c
index c2060203b98af857d510bc6618e2046bf00dc192..396d0f4a259d53f99bd9606e63d4aa52242e4a08 100644 (file)
--- a/fs/gfs2/rgrp.c
+++ b/fs/gfs2/rgrp.c
@@ -2306,7 +2306,7 @@ void gfs2_rgrp_dump(struct seq_file *seq, struct gfs2_rgrpd *rgd,
                       (unsigned long long)rgd->rd_addr, rgd->rd_flags,
                       rgd->rd_free, rgd->rd_free_clone, rgd->rd_dinodes,
                       rgd->rd_requested, rgd->rd_reserved, rgd->rd_extfail_pt);
-       if (rgd->rd_sbd->sd_args.ar_rgrplvb) {
+       if (rgd->rd_sbd->sd_args.ar_rgrplvb && rgd->rd_rgl) {
                struct gfs2_rgrp_lvb *rgl = rgd->rd_rgl;
 
                gfs2_print_dbg(seq, "%s  L: f:%02x b:%u i:%u\n", fs_id_buf,