linux-kernel - [PATCH v3 0/2] iter revert problems

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Message-Id: <cover.1629713020.git.asml.silence@gmail.com>
Date:   Mon, 23 Aug 2021 11:18:43 +0100
From:   Pavel Begunkov <asml.silence@...il.com>
To:     Jens Axboe <axboe@...nel.dk>, io-uring@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Cc:     Palash Oswal <oswalpalash@...il.com>,
        Sudip Mukherjee <sudipm.mukherjee@...il.com>,
        linux-kernel@...r.kernel.org,
        syzbot+9671693590ef5aad8953@...kaller.appspotmail.com,
        asml.silence@...il.com
Subject: [PATCH v3 0/2] iter revert problems

iov_iter_revert() doesn't go well with iov_iter_truncate() in all
cases, see 2/2 for the bug description. As mentioned there the current
problems is because of generic_write_checks(), but there was also a
similar case fixed in 5.12, which should have been triggerable by normal
write(2)/read(2) and others.

It may be better to enforce reexpands as a long term solution, but for
now this patchset is quickier and easier to backport.

v2: don't fail if it was justly fully reverted
v3: use truncated size + reexapand based approach

Pavel Begunkov (2):
  iov_iter: track truncated size
  io_uring: reexpand under-reexpanded iters

 fs/io_uring.c       | 2 ++
 include/linux/uio.h | 6 +++++-
 2 files changed, 7 insertions(+), 1 deletion(-)

-- 
2.32.0