vfs: don't copy things to user space holding the rcu readlock

Oops.  That wasn't very smart.  We don't actually need the RCU lock any
more by the time we copy the cwd string to user space, but I had
stupidly surrounded the whole thing with it.

Introduced by commit 8b19e34188a3 ("vfs: make getcwd() get the root and
pwd path under rcu")

Is-a-big-hairy-idiot: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/fs/dcache.c b/fs/dcache.c
index 99d4d72..29d5821 100644 (file)
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -3067,6 +3067,7 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
                prepend(&cwd, &buflen, "\0", 1);
                error = prepend_path(&pwd, &root, &cwd, &buflen);
                br_read_unlock(&vfsmount_lock);
+               rcu_read_unlock();
 
                if (error < 0)
                        goto out;
@@ -3087,10 +3088,10 @@ SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
                }
        } else {
                br_read_unlock(&vfsmount_lock);
+               rcu_read_unlock();
        }
 
 out:
-       rcu_read_unlock();
        free_page((unsigned long) page);
        return error;
 }