Don't pass pointer to name buffer which is on the stack to another thread,

because the stack might be paged out once the other thread tries to use the
data. Instead, just allocate memory.

MFC after:	2 weeks

1 files changed, 11 insertions, 20 deletions

diff --git a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_dir.c b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_dir.c
index bae9071..6ff9339 100644
--- a/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_dir.c
+++ b/sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_dir.c
@@ -239,15 +239,20 @@ zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name, znode_t **zpp,
 			return (ENOENT);
 		}
 		if (dl == NULL)	{
+			size_t namesize;
+
 			/*
 			 * Allocate a new dirlock and add it to the list.
 			 */
-			dl = kmem_alloc(sizeof (zfs_dirlock_t), KM_SLEEP);
+			namesize = strlen(name) + 1;
+			dl = kmem_alloc(sizeof (zfs_dirlock_t) + namesize,
+			    KM_SLEEP);
 			cv_init(&dl->dl_cv, NULL, CV_DEFAULT, NULL);
-			dl->dl_name = name;
+			dl->dl_name = (char *)(dl + 1);
+			bcopy(name, dl->dl_name, namesize);
 			dl->dl_sharecnt = 0;
 			dl->dl_namelock = 0;
-			dl->dl_namesize = 0;
+			dl->dl_namesize = namesize;
 			dl->dl_dzp = dzp;
 			dl->dl_next = dzp->z_dirlocks;
 			dzp->z_dirlocks = dl;
@@ -264,20 +269,8 @@ zfs_dirent_lock(zfs_dirlock_t **dlpp, znode_t *dzp, char *name, znode_t **zpp,
 	if (flag & ZHAVELOCK)
 		dl->dl_namelock = 1;
 
-	if ((flag & ZSHARED) && ++dl->dl_sharecnt > 1 && dl->dl_namesize == 0) {
-		/*
-		 * We're the second shared reference to dl.  Make a copy of
-		 * dl_name in case the first thread goes away before we do.
-		 * Note that we initialize the new name before storing its
-		 * pointer into dl_name, because the first thread may load
-		 * dl->dl_name at any time.  He'll either see the old value,
-		 * which is his, or the new shared copy; either is OK.
-		 */
-		dl->dl_namesize = strlen(dl->dl_name) + 1;
-		name = kmem_alloc(dl->dl_namesize, KM_SLEEP);
-		bcopy(dl->dl_name, name, dl->dl_namesize);
-		dl->dl_name = name;
-	}
+	if (flag & ZSHARED)
+		dl->dl_sharecnt++;
 
 	mutex_exit(&dzp->z_lock);
 
@@ -361,10 +354,8 @@ zfs_dirent_unlock(zfs_dirlock_t *dl)
 	cv_broadcast(&dl->dl_cv);
 	mutex_exit(&dzp->z_lock);
 
-	if (dl->dl_namesize != 0)
-		kmem_free(dl->dl_name, dl->dl_namesize);
 	cv_destroy(&dl->dl_cv);
-	kmem_free(dl, sizeof (*dl));
+	kmem_free(dl, sizeof (*dl) + dl->dl_namesize);
 }
 
 /*