From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: Kees Cook <keescook@chromium.org>,
Colin Ian King <colin.king@canonical.com>,
Christoph Hellwig <hch@lst.de>,
Johannes Berg <johannes@sipsolutions.net>,
linux-fsdevel <linux-fsdevel@vger.kernel.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: splice() from /dev/zero to a pipe does not work (5.9+)
Date: Fri, 7 May 2021 12:29:44 -0700 [thread overview]
Message-ID: <CAHk-=wjhWKp=fQREgQy0uGjo-uvcTg-11gJLoDp4Af8WOKa8ig@mail.gmail.com> (raw)
In-Reply-To: <YJWSYDk4gAT1hkf6@zeniv-ca.linux.org.uk>
On Fri, May 7, 2021 at 12:17 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Umm... That would do wonders to anything that used to do
> copy_to_user()/clear_user()/copy_to_user() and got converted
> to copy_to_iter()/iov_iter_zero()/copy_to_iter()...
I didn't mean for iov_iter_zero doing this - only splice_read_zero().
> Are you sure we can shove zero page into pipe, anyway?
> IIRC, get_page()/put_page() on that is not allowed,
That's what the
buf->ops = &zero_pipe_buf_ops;
is for. The zero_pipe_buf_ops would have empty get and release
functions, and a 'steal' function that always returns false.
That's how the pipe pages are supposed to work: there are people who
put non-page data (ie things like skbuff allocations etc) into a
splice pipe buffer. It's why we have those "ops" pointers.
Linus
next prev parent reply other threads:[~2021-05-07 19:30 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-07 18:05 splice() from /dev/zero to a pipe does not work (5.9+) Colin Ian King
2021-05-07 18:21 ` Kees Cook
2021-05-07 19:06 ` Linus Torvalds
2021-05-07 19:17 ` Al Viro
2021-05-07 19:29 ` Linus Torvalds [this message]
2021-05-07 20:31 ` Al Viro
2021-05-12 15:13 ` Colin Ian King
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