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SubjectRe: [PATCH] ipmi: Fix I2C client removal in the SSIF driver
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On 08/30/2018 11:44 PM, minyard@acm.org wrote:
>
> From: Corey Minyard <cminyard@mvista.com>
>
> 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:
> kernfs_find_ns+0x28/0x120
> kernfs_find_and_get_ns+0x40/0x60
> sysfs_unmerge_group+0x2c/0x6c
> dpm_sysfs_remove+0x34/0x70
> device_del+0x58/0x30c
> device_unregister+0x30/0x7c
> i2c_unregister_device+0x84/0x90 [i2c_core]
> ssif_platform_remove+0x38/0x98 [ipmi_ssif]
> platform_drv_remove+0x2c/0x6c
> device_release_driver_internal+0x168/0x1f8
> driver_detach+0x50/0xbc
> bus_remove_driver+0x74/0xe8
> driver_unregister+0x34/0x5c
> platform_driver_unregister+0x20/0x2c
> cleanup_ipmi_ssif+0x50/0xd82c [ipmi_ssif]
> __arm64_sys_delete_module+0x1b4/0x220
> el0_svc_handler+0x104/0x160
> 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
> those.
>
> Reported-by: George Cherian <george.cherian@cavium.com>
> Signed-off-by: Corey Minyard <cminyard@mvista.com>
> ---
> 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.

> -corey
>
> 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 {
> struct device *dev;
> struct i2c_client *client;
>
> + struct i2c_client *added_client;
> +
> struct mutex clients_mutex;
> struct list_head clients;
>
> @@ -1639,15 +1641,7 @@ static int ssif_probe(struct i2c_client *client, const struct i2c_device_id *id)
>
> out:
> if (rv) {
> - /*
> - * Note that if addr_info->client is assigned, we
> - * leave it. The i2c client hangs around even if we
> - * 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
> - * don't leave it, ssif_platform_remove will not remove
> - * the client like it should.
> - */
> + addr_info->client = NULL;
> dev_err(&client->dev, "Unable to start IPMI SSIF: %d\n", rv);
> kfree(ssif_info);
> }
> @@ -1667,7 +1661,8 @@ static int ssif_adapter_handler(struct device *adev, void *opaque)
> if (adev->type != &i2c_adapter_type)
> return 0;
>
> - i2c_new_device(to_i2c_adapter(adev), &addr_info->binfo);
> + addr_info->added_client = i2c_new_device(to_i2c_adapter(adev),
> + &addr_info->binfo);
>
> if (!addr_info->adapter_name)
> return 1; /* Only try the first I2C adapter by default. */
> @@ -1840,7 +1835,7 @@ static int ssif_platform_remove(struct platform_device *dev)
> return 0;
>
> mutex_lock(&ssif_infos_mutex);
> - i2c_unregister_device(addr_info->client);
> + i2c_unregister_device(addr_info->added_client);
>
> list_del(&addr_info->link);
> kfree(addr_info);
> --
> 2.7.4
>

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