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SubjectRe: [PATCH] ipmi: Don't allow device module unload when in use
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On 10/14/19 11:46 AM, minyard@acm.org wrote:
> From: Corey Minyard <cminyard@mvista.com>
>
> If something has the IPMI driver open, don't allow the device
> module to be unloaded. Before it would unload and the user would
> get errors on use.
>
> This change is made on user request, and it makes it consistent
> with the I2C driver, which has the same behavior.
>
> It does change things a little bit with respect to kernel users.
> If the ACPI or IPMI watchdog (or any other kernel user) has
> created a user, then the device module cannot be unloaded. Before
> it could be unloaded,
>
> This does not affect hot-plug. If the device goes away (it's on
> something removable that is removed or is hot-removed via sysfs)
> then it still behaves as it did before.
>
> Reported-by: tony camuso <tcamuso@redhat.com>
> Signed-off-by: Corey Minyard <cminyard@mvista.com>
> ---
> Tony, here is a suggested change for this. Can you look it over and
> see if it looks ok?
>
> Thanks,
>
> -corey
>
> drivers/char/ipmi/ipmi_msghandler.c | 23 ++++++++++++++++-------
> include/linux/ipmi_smi.h | 12 ++++++++----
> 2 files changed, 24 insertions(+), 11 deletions(-)

Hi Corey.

You changed ipmi_register_ipmi to ipmi_add_ipmi in ipmi_msghandler, but you
did not change it where it is actually called.

# grep ipmi_register_smi drivers/char/ipmi/*.c
drivers/char/ipmi/ipmi_powernv.c: rc = ipmi_register_smi(&ipmi_powernv_smi_handlers, ipmi, dev, 0);
drivers/char/ipmi/ipmi_si_intf.c: rv = ipmi_register_smi(&handlers,
drivers/char/ipmi/ipmi_ssif.c: rv = ipmi_register_smi(&ssif_info->handlers,

Is there a reason for changing the interface name? Is this something
that I could do instead of troubling you with it?

Regards,
Tony


>
> diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> index 2aab80e19ae0..15680de18625 100644
> --- a/drivers/char/ipmi/ipmi_msghandler.c
> +++ b/drivers/char/ipmi/ipmi_msghandler.c
> @@ -448,6 +448,8 @@ enum ipmi_stat_indexes {
>
> #define IPMI_IPMB_NUM_SEQ 64
> struct ipmi_smi {
> + struct module *owner;
> +
> /* What interface number are we? */
> int intf_num;
>
> @@ -1220,6 +1222,11 @@ int ipmi_create_user(unsigned int if_num,
> if (rv)
> goto out_kfree;
>
> + if (!try_module_get(intf->owner)) {
> + rv = -ENODEV;
> + goto out_kfree;
> + }
> +
> /* Note that each existing user holds a refcount to the interface. */
> kref_get(&intf->refcount);
>
> @@ -1349,6 +1356,7 @@ static void _ipmi_destroy_user(struct ipmi_user *user)
> }
>
> kref_put(&intf->refcount, intf_free);
> + module_put(intf->owner);
> }
>
> int ipmi_destroy_user(struct ipmi_user *user)
> @@ -2459,7 +2467,7 @@ static int __get_device_id(struct ipmi_smi *intf, struct bmc_device *bmc)
> * been recently fetched, this will just use the cached data. Otherwise
> * it will run a new fetch.
> *
> - * Except for the first time this is called (in ipmi_register_smi()),
> + * Except for the first time this is called (in ipmi_add_smi()),
> * this will always return good data;
> */
> static int __bmc_get_device_id(struct ipmi_smi *intf, struct bmc_device *bmc,
> @@ -3377,10 +3385,11 @@ static void redo_bmc_reg(struct work_struct *work)
> kref_put(&intf->refcount, intf_free);
> }
>
> -int ipmi_register_smi(const struct ipmi_smi_handlers *handlers,
> - void *send_info,
> - struct device *si_dev,
> - unsigned char slave_addr)
> +int ipmi_add_smi(struct module *owner,
> + const struct ipmi_smi_handlers *handlers,
> + void *send_info,
> + struct device *si_dev,
> + unsigned char slave_addr)
> {
> int i, j;
> int rv;
> @@ -3406,7 +3415,7 @@ int ipmi_register_smi(const struct ipmi_smi_handlers *handlers,
> return rv;
> }
>
> -
> + intf->owner = owner;
> intf->bmc = &intf->tmp_bmc;
> INIT_LIST_HEAD(&intf->bmc->intfs);
> mutex_init(&intf->bmc->dyn_mutex);
> @@ -3514,7 +3523,7 @@ int ipmi_register_smi(const struct ipmi_smi_handlers *handlers,
>
> return rv;
> }
> -EXPORT_SYMBOL(ipmi_register_smi);
> +EXPORT_SYMBOL(ipmi_add_smi);
>
> static void deliver_smi_err_response(struct ipmi_smi *intf,
> struct ipmi_smi_msg *msg,
> diff --git a/include/linux/ipmi_smi.h b/include/linux/ipmi_smi.h
> index 4dc66157d872..deec18b8944a 100644
> --- a/include/linux/ipmi_smi.h
> +++ b/include/linux/ipmi_smi.h
> @@ -224,10 +224,14 @@ static inline int ipmi_demangle_device_id(uint8_t netfn, uint8_t cmd,
> * is called, and the lower layer must get the interface from that
> * call.
> */
> -int ipmi_register_smi(const struct ipmi_smi_handlers *handlers,
> - void *send_info,
> - struct device *dev,
> - unsigned char slave_addr);
> +int ipmi_add_smi(struct module *owner,
> + const struct ipmi_smi_handlers *handlers,
> + void *send_info,
> + struct device *dev,
> + unsigned char slave_addr);
> +
> +#define ipmi_register_smi(handlers, send_info, dev, slave_addr) \
> + ipmi_add_smi(THIS_MODULE, handlers, send_info, dev, slave_addr)
>
> /*
> * Remove a low-level interface from the IPMI driver. This will
>

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