public inbox for [email protected]
 help / color / mirror / Atom feed
From: Al Viro <[email protected]>
To: Jens Axboe <[email protected]>
Cc: Kyle Huey <[email protected]>,
	open list <[email protected]>,
	Christoph Hellwig <[email protected]>,
	Robert O'Callahan <[email protected]>,
	Andrew Morton <[email protected]>,
	Arnd Bergmann <[email protected]>,
	David Howells <[email protected]>,
	"moderated list:ARM PORT" <[email protected]>,
	"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
	<[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected],
	"open list:FILESYSTEMS (VFS and infrastructure)" 
	<[email protected]>,
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected], [email protected],
	[email protected],
	Linus Torvalds <[email protected]>
Subject: Re: [REGRESSION] mm: process_vm_readv testcase no longer works after compat_prcoess_vm_readv removed
Date: Tue, 27 Oct 2020 00:05:21 +0000	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On Mon, Oct 26, 2020 at 05:56:11PM -0600, Jens Axboe wrote:
> On 10/26/20 4:55 PM, Kyle Huey wrote:
> > A test program from the rr[0] test suite, vm_readv_writev[1], no
> > longer works on 5.10-rc1 when compiled as a 32 bit binary and executed
> > on a 64 bit kernel. The first process_vm_readv call (on line 35) now
> > fails with EFAULT. I have bisected this to
> > c3973b401ef2b0b8005f8074a10e96e3ea093823.
> > 
> > It should be fairly straightforward to extract the test case from our
> > repository into a standalone program.
> 
> Can you check with this applied?
> 
> diff --git a/mm/process_vm_access.c b/mm/process_vm_access.c
> index fd12da80b6f2..05676722d9cd 100644
> --- a/mm/process_vm_access.c
> +++ b/mm/process_vm_access.c
> @@ -273,7 +273,8 @@ static ssize_t process_vm_rw(pid_t pid,
>  		return rc;
>  	if (!iov_iter_count(&iter))
>  		goto free_iov_l;
> -	iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r, false);
> +	iov_r = iovec_from_user(rvec, riovcnt, UIO_FASTIOV, iovstack_r,
> +				in_compat_syscall());

_ouch_

There's a bug, all right, but I'm not sure that this is all there is to it.
For now it's probably the right fix, but...  Consider the fun trying to
use that from 32bit process to access the memory of 64bit one.  IOW, we
might want to add an explicit flag for "force 64bit addresses/sizes
in rvec".

  reply	other threads:[~2020-10-27  0:34 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-10-26 22:55 [REGRESSION] mm: process_vm_readv testcase no longer works after compat_prcoess_vm_readv removed Kyle Huey
2020-10-26 23:56 ` Jens Axboe
2020-10-27  0:05   ` Al Viro [this message]
2020-10-27  0:09     ` Jens Axboe

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    [email protected] \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox