linux-kernel - [BUG] ssb: Possible sleep-in-atomic bugs in ssb_pcmcia

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Date:   Mon, 9 Oct 2017 09:29:17 +0800
From:   Jia-Ju Bai <baijiaju1990@....com>
To:     gregkh@...uxfoundation.org, m@...s.ch, sudipm.mukherjee@...il.com,
        akpm@...ux-foundation.org, johannes@...solutions.net,
        dahinds@...rs.sourceforge.net
Cc:     linux-pcmcia@...ts.infradead.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-wireless@...r.kernel.org
Subject: [BUG] ssb: Possible sleep-in-atomic bugs in ssb_pcmcia_read8

According to pcmcia.c, the driver may sleep under a spinlock.
The function call paths are:
ssb_pcmcia_read8 (acquire the spinlock)
   select_core_and_segment
     ssb_pcmcia_switch_segment
       ssb_pcmcia_cfg_write
         pcmcia_write_config_byte
           pcmcia_access_config (drivers/pcmcia/pcmcia_resource.c)
             mutex_lock --> may sleep

ssb_pcmcia_read8 (acquire the spinlock)
   select_core_and_segment
     ssb_pcmcia_switch_segment
       sssb_pcmcia_cfg_read
         pcmcia_read_config_byte
           pcmcia_access_config (drivers/pcmcia/pcmcia_resource.c)
             mutex_lock --> may sleep

A possible fix is to use spinlock instead of mutex lock in 
pcmcia_access_config in drivers/pcmcia/pcmcia_resource.c.

These bugs are found by my static analysis tool and my code review.


Thanks,
Jia-Ju Bai