linux-kernel - [PATCH] drivers/char/ipmi_si: prevent null deref during module exit

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Date:   Wed, 8 Nov 2017 11:06:03 -0600
From:   Andrew Banman <abanman@....com>
To:     Corey Minyard <minyard@....org>
CC:     Dimitri Sivanich <sivanich@....com>,
        "Anderson, Russ" <russ.anderson@....com>,
        Mike Travis <mike.travis@....com>,
        <openipmi-developer@...ts.sourceforge.net>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH] drivers/char/ipmi_si: prevent null deref during module exit

If there are uninitialized SMIs in the smi_infos list, i.e. with no
handlers set, then disable_si_irq() in cleanup_smi_one() will hit a null
pointer dereference when the former attempts to start the check enables
transaction. Thus, we panic during module exit.

Avoid panicking when there are uninitialized SMIs by checking for a handler
pointer before starting the check enables transaction.

Signed-off-by: Andrew Banman <abanman@....com>
---
  drivers/char/ipmi/ipmi_si_intf.c | 2 +-
  1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/char/ipmi/ipmi_si_intf.c b/drivers/char/ipmi/ipmi_si_intf.c
index cb5719e..6c0b1b3 100644
--- a/drivers/char/ipmi/ipmi_si_intf.c
+++ b/drivers/char/ipmi/ipmi_si_intf.c
@@ -442,7 +442,7 @@ static void start_check_enables(struct smi_info *smi_info, 
bool start_timer)

  	if (start_timer)
  		start_new_msg(smi_info, msg, 2);
-	else
+	else if (smi_info->handlers)
  		smi_info->handlers->start_transaction(smi_info->si_sm, msg, 2);
  	smi_info->si_state = SI_CHECKING_ENABLES;
  }
-- 
1.8.2.1