Re: [PATCH] vfs: Check fd has read access in kernel_read_file_from_fd()

On Thu, Oct 07, 2021 at 11:01:10PM +0100, Matthew Wilcox (Oracle) wrote:

If we open a file without read access and then pass the fd to a syscall whose implementation calls kernel_read_file_from_fd(), we get a warning from __kernel_read():

    if (WARN_ON_ONCE(!(file->f_mode & FMODE_READ)))

This currently affects both finit_module() and kexec_file_load(), but it could affect other syscalls in the future.

Reported-by: Hao Sun sunhao.th@gmail.com Fixes: b844f0ecbc56 ("vfs: define kernel_copy_file_from_fd()") Cc: stable@vger.kernel.org Signed-off-by: Matthew Wilcox (Oracle) willy@infradead.org

Reviewed-by: Kees Cook keescook@chromium.org

Thanks for chasing this down!