In the Linux kernel, the following vulnerability has been resolved: ipmi: si: Fix NULL pointer dereference after failed registration try_s

In the Linux kernel, the following vulnerability has been resolved:

ipmi: si: Fix NULL pointer dereference after failed registration

try_smi_init() allocates new_smi->si_sm and later calls
ipmi_register_smi_mod(), which maps to ipmi_add_smi().

During ipmi_add_smi(), the upper IPMI message handler obtains the
initial BMC device information through __bmc_get_device_id(). This can
fail if the BMC does not return a successful response to the Get Device
ID command.

When the BMC returns a nonzero completion code, the device-id helper
retries the command and eventually returns -EIO if the device ID still
cannot be fetched.

On this failure path, ipmi_add_smi() logs "Unable to get the device id"
and goes to out_err_started, where it invokes the lower driver's
shutdown callback. try_smi_init() then logs the returned registration
failure:

ipmi_si IPI0001:00: IPMI message handler: Unable to get the device id: -5
ipmi_si IPI0001:00: Unable to register device: error -5

For ipmi_si, the shutdown callback is shutdown_smi(), which cleans up
the SI state machine data, frees smi_info->si_sm, and sets
smi_info->si_sm and smi_info->intf to NULL.

However, intf->in_shutdown is not set on this failed-registration
rollback path. Therefore, the asynchronous redo_bmc_reg work item can
still retry BMC device-id probing after the lower driver has already
cleared its SI state machine data. In the observed case, that retry path
reached start_next_msg(), which passed the NULL smi_info->si_sm pointer
to the selected KCS state machine handler:

BUG: unable to handle kernel NULL pointer dereference at 0000000000000000
Workqueue: events redo_bmc_reg [ipmi_msghandler]
RIP: start_kcs_transaction+0x2c/0x190 [ipmi_si]
Call Trace:
start_next_msg+0x50/0x80 [ipmi_si]
check_start_timer_thread.part.9+0x3b/0x50 [ipmi_si]
sender+0x69/0x80 [ipmi_si]
i_ipmi_request+0x2ac/0x9d0 [ipmi_msghandler]
__get_device_id.isra.29+0xaa/0x180 [ipmi_msghandler]
__bmc_get_device_id+0xef/0x950 [ipmi_msghandler]
redo_bmc_reg+0x52/0x60 [ipmi_msghandler]
process_one_work+0x1a7/0x360

Set intf->in_shutdown on the out_err_started path before invoking the
lower driver's shutdown callback. This prevents later redo_bmc_reg
retries from using an interface whose lower driver state has been
cleaned up, and applies the same shutdown state to other IPMI interfaces
as well.