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From: Mike Kravetz <[email protected]>
To: Nadav Amit <[email protected]>, [email protected]
Cc: Nadav Amit <[email protected]>, Jens Axboe <[email protected]>,
	Andrea Arcangeli <[email protected]>,
	Peter Xu <[email protected]>,
	Alexander Viro <[email protected]>,
	[email protected], [email protected],
	[email protected]
Subject: Re: [RFC PATCH 01/13] fs/userfaultfd: fix wrong error code on WP & !VM_MAYWRITE
Date: Tue, 1 Dec 2020 13:22:32 -0800	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 11/28/20 4:45 PM, Nadav Amit wrote:
> From: Nadav Amit <[email protected]>
> 
> It is possible to get an EINVAL error instead of EPERM if the following
> test vm_flags have VM_UFFD_WP but do not have VM_MAYWRITE, as "ret" is
> overwritten since commit cab350afcbc9 ("userfaultfd: hugetlbfs: allow
> registration of ranges containing huge pages").
> 
> Fix it.
> 
> Cc: Mike Kravetz <[email protected]>
> Cc: Jens Axboe <[email protected]>
> Cc: Andrea Arcangeli <[email protected]>
> Cc: Peter Xu <[email protected]>
> Cc: Alexander Viro <[email protected]>
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Cc: [email protected]
> Fixes: cab350afcbc9 ("userfaultfd: hugetlbfs: allow registration of ranges containing huge pages")
> Signed-off-by: Nadav Amit <[email protected]>
> ---
>  fs/userfaultfd.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c
> index 000b457ad087..c8ed4320370e 100644
> --- a/fs/userfaultfd.c
> +++ b/fs/userfaultfd.c
> @@ -1364,6 +1364,7 @@ static int userfaultfd_register(struct userfaultfd_ctx *ctx,
>  			if (end & (vma_hpagesize - 1))
>  				goto out_unlock;
>  		}
> +		ret = -EPERM;
>  		if ((vm_flags & VM_UFFD_WP) && !(cur->vm_flags & VM_MAYWRITE))
>  			goto out_unlock;
>  

Thanks!  We should return EPERM in that case.

However, the check for VM_UFFD_WP && !VM_MAYWRITE went in after commit
cab350afcbc9.  I think it is more accurate to say that the issue was
introduced with commit 63b2d4174c4a ("Introduce the new uffd-wp APIs
for userspace.").  The convention in userfaultfd_register() is that the
return code is set before testing condition which could cause return.
Therefore, when 63b2d4174c4a added the VM_UFFD_WP && !VM_MAYWRITE check,
it should have also added the 'ret = -EPERM;' statement.

With changes to commit message and Fixes tag,

Reviewed-by: Mike Kravetz <[email protected]>
-- 
Mike Kravetz

  reply	other threads:[~2020-12-01 21:23 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-11-29  0:45 [RFC PATCH 00/13] fs/userfaultfd: support iouring and polling Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 01/13] fs/userfaultfd: fix wrong error code on WP & !VM_MAYWRITE Nadav Amit
2020-12-01 21:22   ` Mike Kravetz [this message]
2020-12-21 19:01     ` Peter Xu
2020-11-29  0:45 ` [RFC PATCH 02/13] fs/userfaultfd: fix wrong file usage with iouring Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 03/13] selftests/vm/userfaultfd: wake after copy failure Nadav Amit
2020-12-21 19:28   ` Peter Xu
2020-12-21 19:51     ` Nadav Amit
2020-12-21 20:52       ` Peter Xu
2020-12-21 20:54         ` Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 04/13] fs/userfaultfd: simplify locks in userfaultfd_ctx_read Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 05/13] fs/userfaultfd: introduce UFFD_FEATURE_POLL Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 06/13] iov_iter: support atomic copy_page_from_iter_iovec() Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 07/13] fs/userfaultfd: support read_iter to use io_uring Nadav Amit
2020-11-30 18:20   ` Jens Axboe
2020-11-30 19:23     ` Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 08/13] fs/userfaultfd: complete reads asynchronously Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 09/13] fs/userfaultfd: use iov_iter for copy/zero Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 10/13] fs/userfaultfd: add write_iter() interface Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 11/13] fs/userfaultfd: complete write asynchronously Nadav Amit
2020-12-02  7:12   ` Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 12/13] fs/userfaultfd: kmem-cache for wait-queue objects Nadav Amit
2020-11-30 19:51   ` Nadav Amit
2020-11-29  0:45 ` [RFC PATCH 13/13] selftests/vm/userfaultfd: iouring and polling tests Nadav Amit

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