vfs: don't copy things to user space holding the rcu readlock (ff812d72) · Commits · 戴 / test

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 ("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

+2 −1

Original line number	Diff line number	Diff line
		@@ -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;
		}

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