Re: [PATCH] ipmi: Fix I2C client removal in the SSIF driver

From: Corey Minyard
Date: Fri Aug 31 2018 - 08:13:33 EST

On 08/31/2018 06:58 AM, George Cherian wrote:

On 08/30/2018 11:44 PM, minyard@xxxxxxx wrote:

From: Corey Minyard <cminyard@xxxxxxxxxx>

The SSIF driver was removing any client that came in through the
platform interface, but it should only remove clients that it
added. On a failure in the probe function, this could result
in the following oops when the driver is removed and the
client gets unregistered twice:

 CPU: 107 PID: 30266 Comm: rmmod Not tainted 4.18.0+ #80
 Hardware name: Cavium Inc. Saber/Saber, BIOS Cavium reference firmware version 7.0 08/04/2018
 pstate: 60400009 (nZCv daif +PAN -UAO)
 pc : kernfs_find_ns+0x28/0x120
 lr : kernfs_find_and_get_ns+0x40/0x60
 sp : ffff00002310fb50
 x29: ffff00002310fb50 x28: ffff800a8240f800
 x27: 0000000000000000 x26: 0000000000000000
 x25: 0000000056000000 x24: ffff000009073000
 x23: ffff000008998b38 x22: 0000000000000000
 x21: ffff800ed86de820 x20: 0000000000000000
 x19: ffff00000913a1d8 x18: 0000000000000000
 x17: 0000000000000000 x16: 0000000000000000
 x15: 0000000000000000 x14: 5300737265766972
 x13: 643d4d4554535953 x12: 0000000000000030
 x11: 0000000000000030 x10: 0101010101010101
 x9 : ffff800ea06cc3f9 x8 : 0000000000000000
 x7 : 0000000000000141 x6 : ffff000009073000
 x5 : ffff800adb706b00 x4 : 0000000000000000
 x3 : 00000000ffffffff x2 : 0000000000000000
 x1 : ffff000008998b38 x0 : ffff000008356760
 Process rmmod (pid: 30266, stack limit = 0x00000000e218418d)
 Call trace:
ÂÂ kernfs_find_ns+0x28/0x120
ÂÂ kernfs_find_and_get_ns+0x40/0x60
ÂÂ sysfs_unmerge_group+0x2c/0x6c
ÂÂ dpm_sysfs_remove+0x34/0x70
ÂÂ device_del+0x58/0x30c
ÂÂ device_unregister+0x30/0x7c
ÂÂ i2c_unregister_device+0x84/0x90 [i2c_core]
ÂÂ ssif_platform_remove+0x38/0x98 [ipmi_ssif]
ÂÂ platform_drv_remove+0x2c/0x6c
ÂÂ device_release_driver_internal+0x168/0x1f8
ÂÂ driver_detach+0x50/0xbc
ÂÂ bus_remove_driver+0x74/0xe8
ÂÂ driver_unregister+0x34/0x5c
ÂÂ platform_driver_unregister+0x20/0x2c
ÂÂ cleanup_ipmi_ssif+0x50/0xd82c [ipmi_ssif]
ÂÂ __arm64_sys_delete_module+0x1b4/0x220
ÂÂ el0_svc_handler+0x104/0x160
ÂÂ el0_svc+0x8/0xc
 Code: aa1e03e0 aa0203f6 aa0103f7 d503201f (7940e280)
 ---[ end trace 09f0e34cce8e2d8c ]---
 Kernel panic - not syncing: Fatal exception
 SMP: stopping secondary CPUs
 Kernel Offset: disabled
 CPU features: 0x23800c38

So track the clients that the SSIF driver adds and only remove

Reported-by: George Cherian <george.cherian@xxxxxxxxxx>
Signed-off-by: Corey Minyard <cminyard@xxxxxxxxxx>
 drivers/char/ipmi/ipmi_ssif.c | 17 ++++++-----------
 1 file changed, 6 insertions(+), 11 deletions(-)

George, your fix was close, but not quite right. The following
should fix the problem, obvious in hindsight :-). Thanks for working
with me on this.

Thanks Corey!!!
This works for me now.

Thanks. Can I add a Tested-by: from you?



diff --git a/drivers/char/ipmi/ipmi_ssif.c b/drivers/char/ipmi/ipmi_ssif.c
index e7e8b86..ca4f7c4 100644
--- a/drivers/char/ipmi/ipmi_ssif.c
+++ b/drivers/char/ipmi/ipmi_ssif.c
@@ -182,6 +182,8 @@ struct ssif_addr_info {
ÂÂÂÂÂÂÂÂ struct device *dev;
ÂÂÂÂÂÂÂÂ struct i2c_client *client;

+ÂÂÂÂÂÂ struct i2c_client *added_client;
ÂÂÂÂÂÂÂÂ struct mutex clients_mutex;
ÂÂÂÂÂÂÂÂ struct list_head clients;

@@ -1639,15 +1641,7 @@ static int ssif_probe(struct i2c_client *client, const struct i2c_device_id *id)

ÂÂ out:
ÂÂÂÂÂÂÂÂ if (rv) {
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * Note that if addr_info->client is assigned, we
- * leave it. The i2c client hangs around even if we
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * return a failure here, and the failure here is not
- * propagated back to the i2c code. This seems to be
- * design intent, strange as it may be. But if we
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * don't leave it, ssif_platform_remove will not remove
-ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ * the client like it should.
+ÂÂÂÂÂÂÂÂÂÂÂÂÂÂ addr_info->client = NULL;
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ dev_err(&client->dev, "Unable to start IPMI SSIF: %d\n", rv);
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ kfree(ssif_info);
@@ -1667,7 +1661,8 @@ static int ssif_adapter_handler(struct device *adev, void *opaque)
ÂÂÂÂÂÂÂÂ if (adev->type != &i2c_adapter_type)

-ÂÂÂÂÂÂ i2c_new_device(to_i2c_adapter(adev), &addr_info->binfo);
+ÂÂÂÂÂÂ addr_info->added_client = i2c_new_device(to_i2c_adapter(adev),
+ &addr_info->binfo);

ÂÂÂÂÂÂÂÂ if (!addr_info->adapter_name)
ÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂÂ return 1; /* Only try the first I2C adapter by default. */
@@ -1840,7 +1835,7 @@ static int ssif_platform_remove(struct platform_device *dev)

ÂÂÂÂÂÂÂÂ mutex_lock(&ssif_infos_mutex);
-ÂÂÂÂÂÂ i2c_unregister_device(addr_info->client);
+ÂÂÂÂÂÂ i2c_unregister_device(addr_info->added_client);

ÂÂÂÂÂÂÂÂ list_del(&addr_info->link);
ÂÂÂÂÂÂÂÂ kfree(addr_info);