linux-kernel - Re: [PATCH] eventfs: Have inodes have unique inode numbers

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Message-ID: <CAHk-=whjO4zAmoP8fQkHUQJANahFMZaviNu=Jfd36E=knLPVgQ@mail.gmail.com>
Date: Sun, 28 Jan 2024 20:01:19 -0800
From: Linus Torvalds <torvalds@...ux-foundation.org>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>, 
	LKML <linux-kernel@...r.kernel.org>, 
	Linux Trace Devel <linux-trace-devel@...r.kernel.org>, Christian Brauner <brauner@...nel.org>, 
	Ajay Kaher <ajay.kaher@...adcom.com>, Geert Uytterhoeven <geert@...ux-m68k.org>, 
	linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [PATCH] eventfs: Have inodes have unique inode numbers

On Sun, 28 Jan 2024 at 19:40, Steven Rostedt <rostedt@...dmis.org> wrote:
>
> [  106.258400] BUG: KASAN: slab-use-after-free in tracing_open_file_tr+0x3a/0x120
> [  106.261228] Read of size 8 at addr ffff8881136f27b8 by task cat/868

Are you refcounting the pointers that you have in the dentries (and
inodes)? Like we talked about you needing to do?

Every time you assign a pointer to d_fsdata, you need to kref_get() it.

You try to work around the tracefs weaknesses by trying to clean up
the dentry data, but it's WRONG.

You should refcount the data properly, so that you don't NEED to clean it out.

               Linus