[RFC,v4,45/69] follow_dotdot{,_rcu}(): lift LOOKUP_BENEATH checks out of loop
diff mbox series

Message ID 20200313235357.2646756-45-viro@ZenIV.linux.org.uk
State New
Headers show
Series
  • [RFC,v4,01/69] do_add_mount(): lift lock_mount/unlock_mount into callers
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Commit Message

Al Viro March 13, 2020, 11:53 p.m. UTC
From: Al Viro <viro@zeniv.linux.org.uk>

Behaviour change: LOOKUP_BENEATH lookup of .. in absolute root
yields an error even if it's not the process' root.  That's
possible only if you'd managed to escape chroot jail by way of
procfs symlinks, but IMO the resulting behaviour is not worse -
more consistent and easier to describe:
	".." in root is "stay where you are", uness LOOKUP_BENEATH
	has been given, in which case it's "fail with EXDEV".

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/namei.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

Patch
diff mbox series

diff --git a/fs/namei.c b/fs/namei.c
index 772d82daf3b4..577dc541a4d4 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1370,11 +1370,8 @@  static int follow_dotdot_rcu(struct nameidata *nd)
 	unsigned seq;
 
 	while (1) {
-		if (path_equal(&nd->path, &nd->root)) {
-			if (unlikely(nd->flags & LOOKUP_BENEATH))
-				return -ECHILD;
+		if (path_equal(&nd->path, &nd->root))
 			break;
-		}
 		if (nd->path.dentry != nd->path.mnt->mnt_root) {
 			struct dentry *old = nd->path.dentry;
 
@@ -1405,7 +1402,10 @@  static int follow_dotdot_rcu(struct nameidata *nd)
 			nd->seq = seq;
 		}
 	}
-	if (likely(parent)) {
+	if (unlikely(!parent)) {
+		if (unlikely(nd->flags & LOOKUP_BENEATH))
+			return -ECHILD;
+	} else {
 		nd->path.dentry = parent;
 		nd->seq = seq;
 	}
@@ -1447,11 +1447,8 @@  static int follow_dotdot(struct nameidata *nd)
 {
 	struct dentry *parent = NULL;
 	while (1) {
-		if (path_equal(&nd->path, &nd->root)) {
-			if (unlikely(nd->flags & LOOKUP_BENEATH))
-				return -EXDEV;
+		if (path_equal(&nd->path, &nd->root))
 			break;
-		}
 		if (nd->path.dentry != nd->path.mnt->mnt_root) {
 			/* rare case of legitimate dget_parent()... */
 			parent = dget_parent(nd->path.dentry);
@@ -1466,7 +1463,10 @@  static int follow_dotdot(struct nameidata *nd)
 		if (unlikely(nd->flags & LOOKUP_NO_XDEV))
 			return -EXDEV;
 	}
-	if (likely(parent)) {
+	if (unlikely(!parent)) {
+		if (unlikely(nd->flags & LOOKUP_BENEATH))
+			return -EXDEV;
+	} else {
 		dput(nd->path.dentry);
 		nd->path.dentry = parent;
 	}