linux-kernel - Re: [PATCH 0/2] tracefs: inode alloc/free related fixes

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Message-ID: <20240807093417.4d93b11b@gandalf.local.home>
Date: Wed, 7 Aug 2024 09:34:17 -0400
From: Steven Rostedt <rostedt@...dmis.org>
To: Mathias Krause <minipli@...ecurity.net>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Ajay Kaher <ajay.kaher@...adcom.com>,
 linux-trace-kernel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] tracefs: inode alloc/free related fixes

On Wed,  7 Aug 2024 13:51:37 +0200
Mathias Krause <minipli@...ecurity.net> wrote:

> Hi Steven,
> 
> We ran into yet another tracefs related bug but, fortunately, were able
> to root cause it ourselves.
> 
> The problem only occurs when CONFIG_RANDSTRUCT is enabled and one gets
> (un)lucky to hit a random seed that'll overlay the 'rcu' member of the
> union with a list_head in 'vfs_inode' -- quite unlikely but, apparently,
> we're exceptional "lucky" with our testing ;)
> 
> The first patch is more of an API correctness fix, to bring the tracefs
> inode cache in line with all the other filesystems. The second patch
> actually fixes the bug, which, I think, may also be the cause for what
> Ilkka is seeing[1].

Ah, that would explain it, and why I never triggered it.

> 
> Please apply!

I have an update though.

-- Steve

> 
> Thanks,
> Mathias
> 
> [1] https://lore.kernel.org/all/CAE4VaREzY+a2PvQJYJbfh8DwB4OP7kucZG-e28H22xyWob1w_A@mail.gmail.com/
> 
> Mathias Krause (2):
>   tracefs: Fix inode allocation
>   tracefs: Don't overlay 'struct inode'
> 
>  fs/tracefs/inode.c    | 2 +-
>  fs/tracefs/internal.h | 6 ++----
>  2 files changed, 3 insertions(+), 5 deletions(-)
>