linux-kernel - Re: [PATCH 5.10 147/243] NFSD: Fix TP_printk() format specifier in nfsd_clid

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Date:   Wed, 21 Jul 2021 10:04:13 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Pavel Machek <pavel@...x.de>
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        David Wysochanski <dwysocha@...hat.com>,
        Chuck Lever <chuck.lever@...cle.com>,
        "J. Bruce Fields" <bfields@...hat.com>,
        Sasha Levin <sashal@...nel.org>
Subject: Re: [PATCH 5.10 147/243] NFSD: Fix TP_printk() format specifier in
 nfsd_clid_class

On Tue, 20 Jul 2021 23:48:47 +0200
Pavel Machek <pavel@...x.de> wrote:

> Hi!
> 
> > [ Upstream commit a948b1142cae66785521a389cab2cce74069b547 ]
> > 
> > Since commit 9a6944fee68e ("tracing: Add a verifier to check string
> > pointers for trace events"), which was merged in v5.13-rc1,
> > TP_printk() no longer tacitly supports the "%.*s" format specifier.
> > 
> > These are low value tracepoints, so just remove them.  
> 
> So I understand we want this for mainline, but AFAICT 5.10 does not
> have 9a6944fee68e ("tracing: Add a verifier to check string pointers
> for trace events") commit, so this does not fix any bug and removal of
> tracepoints can be surprising.
>

Thanks for pointing this out. I get so many stable patches, I don't
have time to look at all of them.

Greg, I don't think this should be backported. The verifier code had a
bug in it that broke the '%.*s' formats. This patch removed the good
code because of the broken code.

See eb01f5353bdaa ("tracing: Handle %.*s in trace_check_vprintf()")

-- Steve