vfs - check non-mountpoint dentry might block in __follow_mount_rcu()

When following a mount in rcu-walk mode we must check if the incoming dentry is telling us it may need to block, even if it isn't actually a mountpoint. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

vfs - check non-mountpoint dentry might block in __follow_mount_rcu()
When following a mount in rcu-walk mode we must check if the incoming dentry is telling us it may need to block, even if it isn't actually a mountpoint. Signed-off-by: Ian Kent <raven@themaw.net> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Ian Kent · Al Viro
1 parent b81a618dcd
Showing 1 changed file with 18 additions and 5 deletions Side-by-side Diff
fs/namei.c
@@ -992,6 +992,12 @@
 	return 0;
 }
  
+static inline bool managed_dentry_might_block(struct dentry *dentry)
+{
+	return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
+		dentry->d_op->d_manage(dentry, true) < 0);
+}
+
 /*
  * Skip to top of mountpoint pile in rcuwalk mode.  We abort the rcu-walk if we
  * meet a managed dentry and we're not walking to "..".  True is returned to
  
  
  
@@ -1000,19 +1006,26 @@
 static bool __follow_mount_rcu(struct nameidata *nd, struct path *path,
 			       struct inode **inode, bool reverse_transit)
 {
-	while (d_mountpoint(path->dentry)) {
+	for (;;) {
 		struct vfsmount *mounted;
-		if (unlikely(path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
-		    !reverse_transit &&
-		    path->dentry->d_op->d_manage(path->dentry, true) < 0)
+		/*
+		 * Don't forget we might have a non-mountpoint managed dentry
+		 * that wants to block transit.
+		 */
+		*inode = path->dentry->d_inode;
+		if (!reverse_transit &&
+		     unlikely(managed_dentry_might_block(path->dentry)))
 			return false;
+
+		if (!d_mountpoint(path->dentry))
+			break;
+
 		mounted = __lookup_mnt(path->mnt, path->dentry, 1);
 		if (!mounted)
 			break;
 		path->mnt = mounted;
 		path->dentry = mounted->mnt_root;
 		nd->seq = read_seqcount_begin(&path->dentry->d_seq);
-		*inode = path->dentry->d_inode;
 	}
  
 	if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
...	...	@@ -992,6 +992,12 @@
992	992	return 0;
993	993	}
994	994
	995	+static inline bool managed_dentry_might_block(struct dentry *dentry)
	996	+{
	997	+ return (dentry->d_flags & DCACHE_MANAGE_TRANSIT &&
	998	+ dentry->d_op->d_manage(dentry, true) < 0);
	999	+}
	1000	+
995	1001	/*
996	1002	* Skip to top of mountpoint pile in rcuwalk mode. We abort the rcu-walk if we
997	1003	* meet a managed dentry and we're not walking to "..". True is returned to
998	1004
999	1005
1000	1006
...	...	@@ -1000,19 +1006,26 @@
1000	1006	static bool __follow_mount_rcu(struct nameidata nd, struct path path,
1001	1007	struct inode **inode, bool reverse_transit)
1002	1008	{
1003		- while (d_mountpoint(path->dentry)) {
	1009	+ for (;;) {
1004	1010	struct vfsmount *mounted;
1005		- if (unlikely(path->dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
1006		- !reverse_transit &&
1007		- path->dentry->d_op->d_manage(path->dentry, true) < 0)
	1011	+ /*
	1012	+ * Don't forget we might have a non-mountpoint managed dentry
	1013	+ * that wants to block transit.
	1014	+ */
	1015	+ *inode = path->dentry->d_inode;
	1016	+ if (!reverse_transit &&
	1017	+ unlikely(managed_dentry_might_block(path->dentry)))
1008	1018	return false;
	1019	+
	1020	+ if (!d_mountpoint(path->dentry))
	1021	+ break;
	1022	+
1009	1023	mounted = __lookup_mnt(path->mnt, path->dentry, 1);
1010	1024	if (!mounted)
1011	1025	break;
1012	1026	path->mnt = mounted;
1013	1027	path->dentry = mounted->mnt_root;
1014	1028	nd->seq = read_seqcount_begin(&path->dentry->d_seq);
1015		- *inode = path->dentry->d_inode;
1016	1029	}
1017	1030
1018	1031	if (unlikely(path->dentry->d_flags & DCACHE_NEED_AUTOMOUNT))