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From: Konstantin Belousov <kib@FreeBSD.org>
Date: Fri, 22 Jan 2016 20:30:51 +0000 (UTC)
To: src-committers@freebsd.org, svn-src-all@freebsd.org,
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Subject: svn commit: r294595 - head/sys/fs/devfs
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Author: kib
Date: Fri Jan 22 20:30:51 2016
New Revision: 294595
URL: https://svnweb.freebsd.org/changeset/base/294595

Log:
  When devfs dirent is freed, a vnode might still keep a pointer to it,
  apparently.  Interlock and clear the pointer to avoid free memory
  dereference.
  
  Submitted by:	bde (previous version)
  MFC after:	3 weeks

Modified:
  head/sys/fs/devfs/devfs_devs.c

Modified: head/sys/fs/devfs/devfs_devs.c
==============================================================================
--- head/sys/fs/devfs/devfs_devs.c	Fri Jan 22 20:28:24 2016	(r294594)
+++ head/sys/fs/devfs/devfs_devs.c	Fri Jan 22 20:30:51 2016	(r294595)
@@ -304,6 +304,13 @@ devfs_vmkdir(struct devfs_mount *dmp, ch
 void
 devfs_dirent_free(struct devfs_dirent *de)
 {
+	struct vnode *vp;
+
+	vp = de->de_vnode;
+	mtx_lock(&devfs_de_interlock);
+	if (vp != NULL && vp->v_data == de)
+		vp->v_data = NULL;
+	mtx_unlock(&devfs_de_interlock);
 	free(de, M_DEVFS3);
 }