From: Andreas Gruenbacher <agruenba@redhat.com>
Date: Mon, 11 Mar 2024 14:51:59 +0000 (+0100)
Subject: gfs2: Fix NULL pointer dereference in gfs2_log_flush
X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=35264909e9d1973ab9aaa2a1b07cda70f12bb828;p=linux.git

gfs2: Fix NULL pointer dereference in gfs2_log_flush

In gfs2_jindex_free(), set sdp->sd_jdesc to NULL under the log flush
lock to provide exclusion against gfs2_log_flush().

In gfs2_log_flush(), check if sdp->sd_jdesc is non-NULL before
dereferencing it.  Otherwise, we could run into a NULL pointer
dereference when outstanding glock work races with an unmount
(glock_work_func -> run_queue -> do_xmote -> inode_go_sync ->
gfs2_log_flush).

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
---

diff --git a/fs/gfs2/log.c b/fs/gfs2/log.c
index 8cddf955ebc0c..a6dd68b458cec 100644
--- a/fs/gfs2/log.c
+++ b/fs/gfs2/log.c
@@ -1108,7 +1108,8 @@ repeat:
 	lops_before_commit(sdp, tr);
 	if (gfs2_withdrawing_or_withdrawn(sdp))
 		goto out_withdraw;
-	gfs2_log_submit_bio(&sdp->sd_jdesc->jd_log_bio, REQ_OP_WRITE);
+	if (sdp->sd_jdesc)
+		gfs2_log_submit_bio(&sdp->sd_jdesc->jd_log_bio, REQ_OP_WRITE);
 	if (gfs2_withdrawing_or_withdrawn(sdp))
 		goto out_withdraw;
 
diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c
index e5f79466340d2..9de789b78bc50 100644
--- a/fs/gfs2/super.c
+++ b/fs/gfs2/super.c
@@ -67,9 +67,13 @@ void gfs2_jindex_free(struct gfs2_sbd *sdp)
 	sdp->sd_journals = 0;
 	spin_unlock(&sdp->sd_jindex_spin);
 
+	down_write(&sdp->sd_log_flush_lock);
 	sdp->sd_jdesc = NULL;
+	up_write(&sdp->sd_log_flush_lock);
+
 	while (!list_empty(&list)) {
 		jd = list_first_entry(&list, struct gfs2_jdesc, jd_list);
+		BUG_ON(jd->jd_log_bio);
 		gfs2_free_journal_extents(jd);
 		list_del(&jd->jd_list);
 		iput(jd->jd_inode);