netdev - Re: [PATCH] net/smc: Use a mutex for locking "struct smc

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Message-ID: <9725f86f-eabe-6aaf-0ef1-74138d895834@linux.ibm.com>
Date:   Wed, 23 Feb 2022 18:59:10 +0100
From:   Karsten Graul <kgraul@...ux.ibm.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, linux-s390@...r.kernel.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Tony Lu <tonylu@...ux.alibaba.com>
Cc:     syzbot+4f322a6d84e991c38775@...kaller.appspotmail.com
Subject: Re: [PATCH] net/smc: Use a mutex for locking "struct smc_pnettable"

On 23/02/2022 11:02, Fabio M. De Francesco wrote:
> smc_pnetid_by_table_ib() uses read_lock() and then it calls smc_pnet_apply_ib()
> which, in turn, calls mutex_lock(&smc_ib_devices.mutex).
> 
> read_lock() disables preemption. Therefore, the code acquires a mutex while in
> atomic context and it leads to a SAC bug.
> 
> Fix this bug by replacing the rwlock with a mutex.
> 
> Reported-and-tested-by: syzbot+4f322a6d84e991c38775@...kaller.appspotmail.com
> Fixes: 64e28b52c7a6 ("net/smc: add pnet table namespace support")
> Confirmed-by: Tony Lu <tonylu@...ux.alibaba.com>
> Signed-off-by: Fabio M. De Francesco <fmdefrancesco@...il.com>
> ---

Thank you Fabio!

This should go to the net tree...

Acked-by: Karsten Graul <kgraul@...ux.ibm.com>