vfs: don't copy things to user space holding the rcu readlock
authorLinus Torvalds <torvalds@linux-foundation.org>
Thu, 12 Sep 2013 18:57:01 +0000 (11:57 -0700)
committerLinus Torvalds <torvalds@linux-foundation.org>
Thu, 12 Sep 2013 18:57:01 +0000 (11:57 -0700)
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>

fs/dcache.c

index 99d4d7226203536aaeb2956c6436d7bbc4f69f5c..29d58212aaf02bc039a84ffc7ad998e176a3025c 100644 (file)
@@ -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;
 }