netdev - Re: [PATCH] net: sock: tracing: Fix sock_exceed_buf

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Message-ID: <20220706162113.47275-1-kuniyu@amazon.com>
Date:   Wed, 6 Jul 2022 09:21:13 -0700
From:   Kuniyuki Iwashima <kuniyu@...zon.com>
To:     <rostedt@...dmis.org>
CC:     <davem@...emloft.net>, <edumazet@...gle.com>, <kuniyu@...zon.com>,
        <linux-kernel@...r.kernel.org>, <netdev@...r.kernel.org>,
        <nhorman@...driver.com>
Subject: Re: [PATCH] net: sock: tracing: Fix sock_exceed_buf_limit not to dereference stale pointer

From:   Steven Rostedt <rostedt@...dmis.org>
Date:   Wed, 6 Jul 2022 10:50:40 -0400
> From: "Steven Rostedt (Google)" <rostedt@...dmis.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@...r.kernel.org
> Fixes: 3847ce32aea9f ("core: add tracepoints for queueing skb to rcvbuf")
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>

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

Thanks for shipping the proper fix quickly!