linux-kernel - Re: [PATCH] tracing: Remove precision vsnprintf() check from print event

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Date: Tue, 5 Mar 2024 11:17:49 +0530
From: Sachin Sant <sachinp@...ux.ibm.com>
To: Steven Rostedt <rostedt@...dmis.org>
Cc: LKML <linux-kernel@...r.kernel.org>,
        Linux Trace Kernel <linux-trace-kernel@...r.kernel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] tracing: Remove precision vsnprintf() check from print
 event



> On 05-Mar-2024, at 4:13 AM, Steven Rostedt <rostedt@...dmis.org> wrote:
> 
> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> This reverts 60be76eeabb3d ("tracing: Add size check when printing
> trace_marker output"). The only reason the precision check was added
> was because of a bug that miscalculated the write size of the string into
> the ring buffer and it truncated it removing the terminating nul byte. On
> reading the trace it crashed the kernel. But this was due to the bug in
> the code that happened during development and should never happen in
> practice. If anything, the precision can hide bugs where the string in the
> ring buffer isn't nul terminated and it will not be checked.
> 
> Link: https://lore.kernel.org/all/C7E7AF1A-D30F-4D18-B8E5-AF1EF58004F5@linux.ibm.com/
> Link: https://lore.kernel.org/linux-trace-kernel/20240227125706.04279ac2@gandalf.local.home
> Link: https://lore.kernel.org/all/20240302111244.3a1674be@gandalf.local.home/
> 
> Reported-by: Sachin Sant <sachinp@...ux.ibm.com>
> Fixes: 60be76eeabb3d ("tracing: Add size check when printing trace_marker output")
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
> ---

This fixes the reported problem for me.

All the ftrace selftests complete without any fails.
# of passed:  121
# of failed:  0
# of unresolved:  6
# of untested:  0
# of unsupported:  7
# of xfailed:  1
# of undefined(test bug):  0

Tested-by: Sachin Sant <sachinp@...ux.ibm.com>


— Sachin