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Message-ID: <Zbne_dN3i85JjPxw@infradead.org>
Date: Tue, 30 Jan 2024 21:47:41 -0800
From: Christoph Hellwig <hch@...radead.org>
To: Matthew Wilcox <willy@...radead.org>
Cc: Theodore Ts'o <tytso@....edu>, Dave Chinner <david@...morbit.com>,
syzbot <syzbot+cdee56dbcdf0096ef605@...kaller.appspotmail.com>,
adilger.kernel@...ger.ca, chandan.babu@...cle.com, jack@...e.com,
linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
syzkaller-bugs@...glegroups.com
Subject: Re: current->journal_info got nested! (was Re: [syzbot] [xfs?]
[ext4?] general protection fault in jbd2__journal_start)
On Wed, Jan 31, 2024 at 05:20:10AM +0000, Matthew Wilcox wrote:
> I'd suggest that saving off current->journal_info is risky because
> it might cover a real problem where you've taken a pagefault inside
> a transaction (eg ext4 faulting while in the middle of a transaction on
> the same filesystem that contains the faulting file).
Agreed.
> Seems to me that we shouldn't be writing to userspace while in the
> middle of a transaction. We could even assert that in copy_to_user()?
That sounds useful, but also rather expensive.
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