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From:   Kuniyuki Iwashima <kuniyu@amazon.com>
To:     <rostedt@goodmis.org>
CC:     <davem@davemloft.net>, <edumazet@google.com>, <kuniyu@amazon.com>,
        <linux-kernel@vger.kernel.org>, <netdev@vger.kernel.org>,
        <nhorman@tuxdriver.com>
Subject: Re: [PATCH] net: sock: tracing: Fix sock_exceed_buf_limit not to dereference stale pointer
Date:   Wed, 6 Jul 2022 09:21:13 -0700
Message-ID: <20220706162113.47275-1-kuniyu@amazon.com>
In-Reply-To: <20220706105040.54fc03b0@gandalf.local.home>
References: <20220706105040.54fc03b0@gandalf.local.home>
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From:   Steven Rostedt <rostedt@goodmis.org>
Date:   Wed, 6 Jul 2022 10:50:40 -0400
> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> 
> The trace event sock_exceed_buf_limit saves the prot->sysctl_mem pointer
> and then dereferences it in the TP_printk() portion. This is unsafe as the
> TP_printk() portion is executed at the time the buffer is read. That is,
> it can be seconds, minutes, days, months, even years later. If the proto
> is freed, then this dereference will can also lead to a kernel crash.
> 
> Instead, save the sysctl_mem array into the ring buffer and have the
> TP_printk() reference that instead. This is the proper and safe way to
> read pointers in trace events.
> 
> Link: https://lore.kernel.org/all/20220706052130.16368-12-kuniyu@amazon.com/
> 
> Cc: stable@vger.kernel.org
> Fixes: 3847ce32aea9f ("core: add tracepoints for queueing skb to rcvbuf")
> Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>

Acked-by: Kuniyuki Iwashima <kuniyu@amazon.com>

Thanks for shipping the proper fix quickly!