• Tycho Andersen's avatar
    seccomp: fix UAF in user-trap code · a811dc61
    Tycho Andersen authored
    On the failure path, we do an fput() of the listener fd if the filter fails
    to install (e.g. because of a TSYNC race that's lost, or if the thread is
    killed, etc.). fput() doesn't actually release the fd, it just ads it to a
    work queue. Then the thread proceeds to free the filter, even though the
    listener struct file has a reference to it.
    
    To fix this, on the failure path let's set the private data to null, so we
    know in ->release() to ignore the filter.
    
    Reported-by: syzbot+981c26489b2d1c6316ba@syzkaller.appspotmail.com
    Fixes: 6a21cc50 ("seccomp: add a return code to trap to userspace")
    Signed-off-by: 's avatarTycho Andersen <tycho@tycho.ws>
    Acked-by: 's avatarKees Cook <keescook@chromium.org>
    Signed-off-by: 's avatarJames Morris <james.morris@microsoft.com>
    a811dc61