From ca99c1da080345e227cfb083c330a184d42e27f3 Mon Sep 17 00:00:00 2001 From: Dipankar Sarma Date: Tue, 18 Apr 2006 22:21:46 -0700 Subject: [PATCH] Fix file lookup without ref There are places in the kernel where we look up files in fd tables and access the file structure without holding refereces to the file. So, we need special care to avoid the race between looking up files in the fd table and tearing down of the file in another CPU. Otherwise, one might see a NULL f_dentry or such torn down version of the file. This patch fixes those special places where such a race may happen. Signed-off-by: Dipankar Sarma Acked-by: "Paul E. McKenney" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- drivers/char/tty_io.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) (limited to 'drivers/char') diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c index 841f0bd3eaa..f07637a8f88 100644 --- a/drivers/char/tty_io.c +++ b/drivers/char/tty_io.c @@ -2723,7 +2723,11 @@ static void __do_SAK(void *arg) } task_lock(p); if (p->files) { - rcu_read_lock(); + /* + * We don't take a ref to the file, so we must + * hold ->file_lock instead. + */ + spin_lock(&p->files->file_lock); fdt = files_fdtable(p->files); for (i=0; i < fdt->max_fds; i++) { filp = fcheck_files(p->files, i); @@ -2738,7 +2742,7 @@ static void __do_SAK(void *arg) break; } } - rcu_read_unlock(); + spin_unlock(&p->files->file_lock); } task_unlock(p); } while_each_thread(g, p); -- cgit v1.2.3