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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Al Viro <viro@zeniv.linux.org.uk>
Cc: cluster-devel <cluster-devel@redhat.com>, Jan Kara <jack@suse.cz>,
	Andreas Gruenbacher <agruenba@redhat.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	Christoph Hellwig <hch@infradead.org>,
	linux-fsdevel <linux-fsdevel@vger.kernel.org>,
	ocfs2-devel@oss.oracle.com
Subject: Re: [Ocfs2-devel] [PATCH v7 05/19] iov_iter: Introduce fault_in_iov_iter_writeable
Date: Fri, 27 Aug 2021 12:33:00 -0700	[thread overview]
Message-ID: <CAHk-=wjMyZLH+ta5SohAViSc10iPj-hRnHc-KPDoj1XZCmxdBg@mail.gmail.com> (raw)
In-Reply-To: <YSk7xfcHVc7CxtQO@zeniv-ca.linux.org.uk>

On Fri, Aug 27, 2021 at 12:23 PM Al Viro <viro@zeniv.linux.org.uk> wrote:
>
> Could you show the cases where "partial copy, so it's OK" behaviour would
> break anything?

Absolutely.

For example, i t would cause an infinite loop in
restore_fpregs_from_user() if the "buf" argument is a situation where
the first page is fine, but the next page is not.

Why? Because __restore_fpregs_from_user() would take a fault, but then
fault_in_pages_readable() (renamed) would succeed, so you'd just do
that "retry" forever and ever.

Probably there are a number of other places too. That was literally
the *first* place I looked at.

Seriously. The current semantics are "check the whole area".

THOSE MUST NOT CHANGE.

              Linus

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  reply	other threads:[~2021-08-27 19:33 UTC|newest]

Thread overview: 100+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-27 16:49 [Ocfs2-devel] [PATCH v7 00/19] gfs2: Fix mmap + page fault deadlocks Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 01/19] iov_iter: Fix iov_iter_get_pages{, _alloc} page fault return value Andreas Gruenbacher
2021-09-09 11:09   ` Christoph Hellwig
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 02/19] powerpc/kvm: Fix kvm_use_magic_page Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 03/19] gup: Turn fault_in_pages_{readable, writeable} into fault_in_{readable, writeable} Andreas Gruenbacher
2021-08-27 19:08   ` Al Viro
2021-09-03 14:56   ` Filipe Manana
2021-09-28 15:02     ` Andreas Gruenbacher
2021-09-28 16:37       ` Matthew Wilcox
2021-09-28 20:41         ` Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 04/19] iov_iter: Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable Andreas Gruenbacher
2021-08-27 18:53   ` Al Viro
2021-08-27 18:57     ` Linus Torvalds
2021-08-27 19:16       ` Al Viro
2021-08-27 20:56   ` Kari Argillander
2021-08-28 17:13     ` Linus Torvalds
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 05/19] iov_iter: Introduce fault_in_iov_iter_writeable Andreas Gruenbacher
2021-08-27 18:49   ` Al Viro
2021-08-27 19:05     ` Linus Torvalds
2021-08-27 19:23       ` Al Viro
2021-08-27 19:33         ` Linus Torvalds [this message]
2021-08-27 19:37           ` Al Viro
2021-08-27 21:48             ` Al Viro
2021-08-27 21:57               ` Al Viro
2021-08-27 23:22                 ` Luck, Tony
2021-08-28  2:20                   ` Luck, Tony
2021-08-28 21:47                   ` Thomas Gleixner
2021-08-28 22:04                     ` Al Viro
2021-08-28 22:11                       ` Al Viro
2021-08-28 22:19                         ` Al Viro
2021-08-28 22:51                           ` Al Viro
2021-08-29 18:44                             ` Thomas Gleixner
2021-08-29 19:46                               ` Al Viro
2021-08-29 19:51                                 ` Thomas Gleixner
2021-08-28 22:20                         ` Tony Luck
2021-08-29  1:40                           ` Matthew Wilcox
2021-08-30 15:41                             ` Luck, Tony
2021-08-28 22:23                       ` Thomas Gleixner
2021-08-28 19:28               ` [Ocfs2-devel] [RFC][arm64] possible infinite loop in btrfs search_ioctl() Al Viro
2021-08-31 13:54                 ` Catalin Marinas
2021-08-31 15:28                   ` Al Viro
2021-08-31 16:01                     ` Catalin Marinas
2021-10-11 17:37                     ` Catalin Marinas
2021-10-11 19:15                       ` Linus Torvalds
2021-10-11 21:08                         ` Catalin Marinas
2021-10-11 23:59                           ` Linus Torvalds
2021-10-12 17:27                             ` Catalin Marinas
2021-10-12 17:58                               ` Linus Torvalds
2021-10-18 17:13                                 ` Catalin Marinas
2021-10-21  0:46                             ` Andreas Gruenbacher
2021-10-21 10:05                               ` Catalin Marinas
2021-10-21 14:42                                 ` Andreas Gruenbacher
2021-10-21 17:09                                   ` Catalin Marinas
2021-10-21 18:00                                     ` Andreas Gruenbacher
2021-10-22 18:41                                       ` Catalin Marinas
2021-10-25 19:37                                         ` Andreas Gruenbacher
2021-10-22  2:30                                   ` Linus Torvalds
2021-10-22  9:34                                     ` Catalin Marinas
2021-08-29  0:58               ` [Ocfs2-devel] [PATCH v7 05/19] iov_iter: Introduce fault_in_iov_iter_writeable Al Viro
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 06/19] gfs2: Add wrapper for iomap_file_buffered_write Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 07/19] gfs2: Clean up function may_grant Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 08/19] gfs2: Eliminate vestigial HIF_FIRST Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 09/19] gfs2: Remove redundant check from gfs2_glock_dq Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 10/19] gfs2: Introduce flag for glock holder auto-demotion Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 11/19] gfs2: Move the inode glock locking to gfs2_file_buffered_write Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 12/19] gfs2: Eliminate ip->i_gh Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 13/19] gfs2: Fix mmap + page fault deadlocks for buffered I/O Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 14/19] iomap: Fix iomap_dio_rw return value for user copies Andreas Gruenbacher
2021-09-03 18:54   ` Darrick J. Wong
2021-09-09 11:17   ` Christoph Hellwig
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 15/19] iomap: Support partial direct I/O on user copy failures Andreas Gruenbacher
2021-09-03 18:54   ` Darrick J. Wong
2021-09-09 11:20   ` Christoph Hellwig
2021-09-28 15:05     ` Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 16/19] iomap: Add done_before argument to iomap_dio_rw Andreas Gruenbacher
2021-08-27 18:30   ` Darrick J. Wong
2021-08-27 20:15     ` Andreas Gruenbacher
2021-08-27 21:32       ` Darrick J. Wong
2021-08-27 21:49         ` Andreas Grünbacher
2021-08-27 22:35         ` Linus Torvalds
2021-09-03 18:47           ` Darrick J. Wong
2021-09-03 18:53   ` Darrick J. Wong
2021-09-09 11:30   ` Christoph Hellwig
2021-09-09 17:22     ` Linus Torvalds
2021-09-10  7:36       ` Christoph Hellwig
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 17/19] gup: Introduce FOLL_NOFAULT flag to disable page faults Andreas Gruenbacher
2021-09-09 11:36   ` Christoph Hellwig
2021-09-09 17:17     ` Linus Torvalds
2021-09-10  7:24       ` Christoph Hellwig
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 18/19] iov_iter: Introduce nofault " Andreas Gruenbacher
2021-08-27 18:47   ` Al Viro
2021-08-27 19:56     ` Andreas Gruenbacher
2021-08-27 16:49 ` [Ocfs2-devel] [PATCH v7 19/19] gfs2: Fix mmap + page fault deadlocks for direct I/O Andreas Gruenbacher
2021-08-27 17:16 ` [Ocfs2-devel] [PATCH v7 00/19] gfs2: Fix mmap + page fault deadlocks Linus Torvalds
2021-09-01 19:52   ` Andreas Gruenbacher
2021-09-03 15:52     ` Linus Torvalds
2021-09-03 18:25       ` Al Viro
2021-09-03 18:47         ` Linus Torvalds
2021-09-03 19:51       ` Andreas Grünbacher
2021-09-03 15:07 ` Filipe Manana

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