CVE-2026-81005: Linux kernel · ipmi: si: Fix NULL pointer dereference after failed registration

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.

• nvd.nist.gov/vuln/detail/CVE-2026-81005 (opens in a new tab)
• git.kernel.org/stable/c/53af3a8bae0a93c1342e1b5519812203332aca8e (opens in a new tab)
• git.kernel.org/stable/c/6d920a75df9a83ab096b3cde7a643b656e4fdfeb (opens in a new tab)
• git.kernel.org/stable/c/8ada17dd4c4ffd6b94621e735d77eda196ce118f (opens in a new tab)
• git.kernel.org/stable/c/d4be659a3e56f4eb16039ab8a1162efea086a714 (opens in a new tab)
• msrc.microsoft.com/csaf/vex/2026/msrc_cve-2026-81005.json (opens in a new tab)
• support.microsoft.com/lifecycle (opens in a new tab)
• first.org/cvss (opens in a new tab)
• ubuntu.com/security/CVE-2026-81005 (opens in a new tab)
• cve.org/CVERecord?id=CVE-2026-81005 (opens in a new tab)
• git.kernel.org/linus/6d920a75df9a83ab096b3cde7a643b656e4fdfeb (opens in a new tab)

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