On Wed, Oct 18, 2017 at 10:32:30PM +0200, Krzysztof Opasiak wrote:
> @@ -417,7 +417,7 @@ static int task_get_unused_fd_flags(struct binder_proc *proc, int flags)
> rlim_cur = task_rlimit(proc->tsk, RLIMIT_NOFILE);
> unlock_task_sighand(proc->tsk, &irqs);
>
> - return __alloc_fd(files, 0, rlim_cur, flags);
> + return __alloc_fd(proc->tsk, 0, rlim_cur, flags);
Who said that proc->files will remain equal to proc->tsk->files?
> -static void __put_unused_fd(struct files_struct *files, unsigned int fd)
> +static void __put_unused_fd(struct task_struct *owner, unsigned int fd)
> {
> + struct files_struct *files = owner->files;
> struct fdtable *fdt = files_fdtable(files);
> __clear_open_fd(fd, fdt);
> if (fd < files->next_fd)
> files->next_fd = fd;
> +
> + if (rlimit_noti_watch_active(owner, RLIMIT_NOFILE)) {
> + unsigned int count;
> +
> + count = count_open_fds(fdt);
> + rlimit_noti_res_changed(owner, RLIMIT_NOFILE, count + 1, count);
> + }
> }
[... and similar for other __...fd() primitives]
This is blatantly wrong - you *CAN'T* modify files_struct unless it's
a) yours (i.e. current->files) or
b) you've had its refcount incremented for you by some process that
did, at the time, have current->files pointing to it.
There is a reason why binder keeps ->files explicitly, rather than going through
->tsk->files.
