On 12/16, Andrew Vagin wrote:
>
> Signed-off-by: Andrew Vagin <avagin@xxxxxxxxxx>
Nice changelog ;)
I agree with Tejun, this doesn't look like the good idea to me...
As for the patch itself,
> @@ -826,6 +827,32 @@ int ptrace_request(struct task_struct *child, long request,
> break;
> }
> #endif
> + case PTRACE_DUPFD:
> + {
> + struct file *file = fget_raw(data);
> + ret = -EBADF;
> +
> + if (!file)
> + break;
> +
> + task_lock(child);
> + if (!child->files)
> + goto out_getfd;
> +
> + ret = alloc_task_fd(child, 0, 0);
alloc_fdtable() does kmalloc(GFP_KERNEL)/vmalloc(), not good under
spin_lock().
> + if (ret < 0) {
> + fput(file);
We can't do this under task_lock() too.
A tracer's sub-thread (or any CLONE_FILES task) can close this file,
it is possible that we have the last reference.
Probably, instead of the new *_task_* helpers, you can add
alloc_file_fd/fd_files_install which take the result of
get_files_struct() as the additional argument. This way you can
avoid task_lock().
Oleg.
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