fs: prevent out-of-bounds array speculation when closing a file descriptor

Google-Bug-Id: 114199369
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/file.c b/fs/file.c
index c942c89..7893ea1 100644 (file)
--- a/fs/file.c
+++ b/fs/file.c
@@ -642,6 +642,7 @@ static struct file *pick_file(struct files_struct *files, unsigned fd)
        if (fd >= fdt->max_fds)
                return NULL;
 
+       fd = array_index_nospec(fd, fdt->max_fds);
        file = fdt->fd[fd];
        if (file) {
                rcu_assign_pointer(fdt->fd[fd], NULL);