fix open/umount race
nameidata_to_filp() drops nd->path or transfers it to opened
file. In the former case it's a Bad Idea(tm) to do mnt_drop_write()
on nd->path.mnt, since we might race with umount and vfsmount in
question might be gone already.
Fix: don't drop it, then... IOW, have nameidata_to_filp() grab nd->path
in case it transfers it to file and do path_drop() in callers. After
they are through with accessing nd->path...
Reported-by: Miklos Szeredi <miklos@szeredi.hu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/open.c b/fs/open.c
index d74e198..4197b9e 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -786,11 +786,11 @@
/* Pick up the filp from the open intent */
filp = nd->intent.open.file;
/* Has the filesystem initialised the file for us? */
- if (filp->f_path.dentry == NULL)
+ if (filp->f_path.dentry == NULL) {
+ path_get(&nd->path);
filp = __dentry_open(nd->path.dentry, nd->path.mnt, filp,
NULL, cred);
- else
- path_put(&nd->path);
+ }
return filp;
}