Commit d22f69a0 authored Apr 24, 2020 by Bob Peterson Committed by Andreas Gruenbacher May 08, 2020

gfs2: Fix use-after-free in gfs2_logd after withdraw



When the gfs2_logd daemon withdrew, the withdraw sequence called
into make_fs_ro() to make the file system read-only. That caused the
journal descriptors to be freed. However, those journal descriptors
were used by gfs2_logd's call to gfs2_ail_flush_reqd(). This caused
a use-after free and NULL pointer dereference.

This patch changes function gfs2_logd() so that it stops all logd
work until the thread is told to stop. Once a withdraw is done,
it only does an interruptible sleep.

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

parent 53af80ce

fs/gfs2/log.c

+5 −0

Original line number	Diff line number	Diff line
		@@ -1131,6 +1131,10 @@ int gfs2_logd(void *data)

		while (!kthread_should_stop()) {

		if (gfs2_withdrawn(sdp)) {
		msleep_interruptible(HZ);
		continue;
		}
		/* Check for errors writing to the journal */
		if (sdp->sd_log_error) {
		gfs2_lm(sdp,
		@@ -1139,6 +1143,7 @@ int gfs2_logd(void *data)
		"prevent further damage.\n",
		sdp->sd_fsname, sdp->sd_log_error);
		gfs2_withdraw(sdp);
		continue;
		}

		did_flush = false;