linux-kernel - Re: [PATCH AUTOSEL 5.4 30/73] futex: Fix inode life-time issue

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Message-ID: <20200324080633.GA2016351@kroah.com>
Date:   Tue, 24 Mar 2020 09:06:33 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Jann Horn <jannh@...gle.com>
Cc:     Sasha Levin <sashal@...nel.org>, stable <stable@...r.kernel.org>,
        kernel list <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH AUTOSEL 5.4 30/73] futex: Fix inode life-time issue

On Mon, Mar 23, 2020 at 08:18:04PM +0100, Jann Horn wrote:
> On Wed, Mar 18, 2020 at 9:54 PM Sasha Levin <sashal@...nel.org> wrote:
> >
> > From: Peter Zijlstra <peterz@...radead.org>
> >
> > [ Upstream commit 8019ad13ef7f64be44d4f892af9c840179009254 ]
> >
> > As reported by Jann, ihold() does not in fact guarantee inode
> > persistence. And instead of making it so, replace the usage of inode
> > pointers with a per boot, machine wide, unique inode identifier.
> >
> > This sequence number is global, but shared (file backed) futexes are
> > rare enough that this should not become a performance issue.
> 
> Please also take this patch, together with
> 8d67743653dce5a0e7aa500fcccb237cde7ad88e "futex: Unbreak futex
> hashing", into the older stable branches. This has to go all the way
> back; as far as I can tell, the bug already existed at the beginning
> of git history.

I have queued these up now, thanks for the hint.

greg k-h