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[RFC,v4,33/69] atomic_open(): return the right dentry in FMODE_OPENED case

Message ID 20200313235357.2646756-33-viro@ZenIV.linux.org.uk (mailing list archive)
State New, archived
Headers show
Series [RFC,v4,01/69] do_add_mount(): lift lock_mount/unlock_mount into callers | expand

Commit Message

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

->atomic_open() might have used a different alias than the one we'd
passed to it; in "not opened" case we take care of that, in "opened"
one we don't.  Currently we don't care downstream of "opened" case
which alias to return; however, that will change shortly when we
get to unifying may_open() calls.

It's not hard to get right in all cases, anyway.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
---
 fs/namei.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
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Patch

diff --git a/fs/namei.c b/fs/namei.c
index 40d5f7abfa54..88f985aff4f8 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2949,11 +2949,15 @@  static struct dentry *atomic_open(struct nameidata *nd, struct dentry *dentry,
 	d_lookup_done(dentry);
 	if (!error) {
 		if (file->f_mode & FMODE_OPENED) {
+			int acc_mode = op->acc_mode;
+			if (unlikely(dentry != file->f_path.dentry)) {
+				dput(dentry);
+				dentry = dget(file->f_path.dentry);
+			}
 			/*
 			 * We didn't have the inode before the open, so check open
 			 * permission here.
 			 */
-			int acc_mode = op->acc_mode;
 			if (file->f_mode & FMODE_CREATED) {
 				WARN_ON(!(open_flag & O_CREAT));
 				fsnotify_create(dir, dentry);