linux-kernel - [PATCH 2/2] ipmi_ssif: Fix crash seen while ipmi_unregister

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Message-Id: <1535109010-5074-2-git-send-email-george.cherian@cavium.com>
Date:   Fri, 24 Aug 2018 04:10:10 -0700
From:   George Cherian <george.cherian@...ium.com>
To:     linux-kernel@...r.kernel.org,
        openipmi-developer@...ts.sourceforge.net
Cc:     minyard@....org, arnd@...db.de, gregkh@...uxfoundation.org,
        George Cherian <george.cherian@...ium.com>
Subject: [PATCH 2/2] ipmi_ssif: Fix crash seen while ipmi_unregister_smi

Dont set ssif_info->intf to NULL before ipmi_unresgiter_smi.
shutdown_ssif will anyways free ssif_info.

Following crash is obsearved if ssif_info->intf is set to NULL
before ipmi_unregister_smi.

 CPU: 119 PID: 7317 Comm: kssif000e Not tainted 4.18.0+ #80
 Hardware name: Cavium Inc. Saber/Saber, BIOS Cavium reference firmware version 7.0 08/04/2018
 pstate: 20400009 (nzCv daif +PAN -UAO)
 pc : ipmi_smi_msg_received+0x44/0x3bc [ipmi_msghandler]
 lr : deliver_recv_msg+0x30/0x5c [ipmi_ssif]
 sp : ffff000037a0fd20
 x29: ffff000037a0fd20 x28: 0000000000000000
 x27: ffff0000047e08f0 x26: ffff800ed9375800
 x25: ffff000037a0fe00 x24: ffff000009073000
 x23: 0000000000000013 x22: 0000000000000000
 x21: 0000000000007000 x20: ffff800adce18400
 x19: 0000000000000000 x18: ffff00003742fd38
 x17: ffff0000089960f0 x16: 000000000000000e
 x15: 0000000000000007 x14: 0000000000000000
 x13: 0000000000000000 x12: 0000000000000033
 x11: 0000000000000381 x10: 0000000000000ba0
 x9 : 0000000000000000 x8 : ffff800ac001fc00
 x7 : ffff7fe003b4d800 x6 : ffff800adce1854b
 x5 : 0000000000000014 x4 : 0000000000000004
 x3 : 0000000000000000 x2 : 0000000000000002
 x1 : 567cb12f8b916b00 x0 : 0000000000000002
 Process kssif000e (pid: 7317, stack limit = 0x0000000041077d8a)
 Call trace:
  ipmi_smi_msg_received+0x44/0x3bc [ipmi_msghandler]
  deliver_recv_msg+0x30/0x5c [ipmi_ssif]
  msg_done_handler+0x2f0/0x66c [ipmi_ssif]
  ipmi_ssif_thread+0x108/0x124 [ipmi_ssif]
  kthread+0x108/0x134
  ret_from_fork+0x10/0x18
 Code: b9402280 91401e75 f90037a1 7100041f (b945bab6)
 ---[ end trace fb7d748bc7b17490 ]---
 Kernel panic - not syncing: Fatal exception
 SMP: stopping secondary CPUs
 Kernel Offset: disabled
 CPU features: 0x23800c38
 Memory Limit: none
 ---[ end Kernel panic - not syncing: Fatal exception ]---

Signed-off-by: George Cherian <george.cherian@...ium.com>
---
 drivers/char/ipmi/ipmi_ssif.c | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/drivers/char/ipmi/ipmi_ssif.c b/drivers/char/ipmi/ipmi_ssif.c
index ccdf6b1..1490636 100644
--- a/drivers/char/ipmi/ipmi_ssif.c
+++ b/drivers/char/ipmi/ipmi_ssif.c
@@ -1226,7 +1226,6 @@ static void shutdown_ssif(void *send_info)
 static int ssif_remove(struct i2c_client *client)
 {
 	struct ssif_info *ssif_info = i2c_get_clientdata(client);
-	struct ipmi_smi *intf;
 	struct ssif_addr_info *addr_info;
 
 	if (!ssif_info)
@@ -1236,9 +1235,7 @@ static int ssif_remove(struct i2c_client *client)
 	 * After this point, we won't deliver anything asychronously
 	 * to the message handler.  We can unregister ourself.
 	 */
-	intf = ssif_info->intf;
-	ssif_info->intf = NULL;
-	ipmi_unregister_smi(intf);
+	ipmi_unregister_smi(ssif_info->intf);
 
 	list_for_each_entry(addr_info, &ssif_infos, link) {
 		if (addr_info->client == client) {
-- 
1.8.3.1