diff mbox series

[RFC,v3,43/55] follow_dotdot{,_rcu}(): lift LOOKUP_BENEATH checks out of loop

Message ID 20200301215240.873899-43-viro@ZenIV.linux.org.uk (mailing list archive)
State New, archived
Headers show
Series [RFC,v3,01/55] do_add_mount(): lift lock_mount/unlock_mount into callers | expand

Commit Message

Al Viro March 1, 2020, 9:52 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(-)
diff mbox series

Patch

diff --git a/fs/namei.c b/fs/namei.c
index c307bf7cbaa1..be756aa32240 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;
 	}