From 7d6380cd40f7993f75c4bde5b36f6019237e8719 Mon Sep 17 00:00:00 2001 From: Corey Minyard Date: Fri, 16 Nov 2018 09:59:21 -0600 Subject: [PATCH 1/5] ipmi:ssif: Fix handling of multi-part return messages The block number was not being compared right, it was off by one when checking the response. Some statistics wouldn't be incremented properly in some cases. Check to see if that middle-part messages always have 31 bytes of data. Signed-off-by: Corey Minyard Cc: stable@vger.kernel.org # 4.4 --- drivers/char/ipmi/ipmi_ssif.c | 25 +++++++++++++++++-------- 1 file changed, 17 insertions(+), 8 deletions(-) diff --git a/drivers/char/ipmi/ipmi_ssif.c b/drivers/char/ipmi/ipmi_ssif.c index ca9528c4f183..b7a1ae2afaea 100644 --- a/drivers/char/ipmi/ipmi_ssif.c +++ b/drivers/char/ipmi/ipmi_ssif.c @@ -632,8 +632,9 @@ static void msg_done_handler(struct ssif_info *ssif_info, int result, /* Remove the multi-part read marker. */ len -= 2; + data += 2; for (i = 0; i < len; i++) - ssif_info->data[i] = data[i+2]; + ssif_info->data[i] = data[i]; ssif_info->multi_len = len; ssif_info->multi_pos = 1; @@ -661,8 +662,19 @@ static void msg_done_handler(struct ssif_info *ssif_info, int result, } blocknum = data[0]; + len--; + data++; - if (ssif_info->multi_len + len - 1 > IPMI_MAX_MSG_LENGTH) { + if (blocknum != 0xff && len != 31) { + /* All blocks but the last must have 31 data bytes. */ + result = -EIO; + if (ssif_info->ssif_debug & SSIF_DEBUG_MSG) + pr_info("Received middle message <31\n"); + + goto continue_op; + } + + if (ssif_info->multi_len + len > IPMI_MAX_MSG_LENGTH) { /* Received message too big, abort the operation. */ result = -E2BIG; if (ssif_info->ssif_debug & SSIF_DEBUG_MSG) @@ -671,16 +683,14 @@ static void msg_done_handler(struct ssif_info *ssif_info, int result, goto continue_op; } - /* Remove the blocknum from the data. */ - len--; for (i = 0; i < len; i++) - ssif_info->data[i + ssif_info->multi_len] = data[i + 1]; + ssif_info->data[i + ssif_info->multi_len] = data[i]; ssif_info->multi_len += len; if (blocknum == 0xff) { /* End of read */ len = ssif_info->multi_len; data = ssif_info->data; - } else if (blocknum + 1 != ssif_info->multi_pos) { + } else if (blocknum != ssif_info->multi_pos) { /* * Out of sequence block, just abort. Block * numbers start at zero for the second block, @@ -707,6 +717,7 @@ static void msg_done_handler(struct ssif_info *ssif_info, int result, } } + continue_op: if (result < 0) { ssif_inc_stat(ssif_info, receive_errors); } else { @@ -714,8 +725,6 @@ static void msg_done_handler(struct ssif_info *ssif_info, int result, ssif_inc_stat(ssif_info, received_message_parts); } - - continue_op: if (ssif_info->ssif_debug & SSIF_DEBUG_STATE) pr_info("DONE 1: state = %d, result=%d\n", ssif_info->ssif_state, result); From a7102c7461794a5bb31af24b08e9e0f50038897a Mon Sep 17 00:00:00 2001 From: "Gustavo A. R. Silva" Date: Wed, 9 Jan 2019 17:39:06 -0600 Subject: [PATCH 2/5] ipmi: msghandler: Fix potential Spectre v1 vulnerabilities channel and addr->channel are indirectly controlled by user-space, hence leading to a potential exploitation of the Spectre variant 1 vulnerability. These issues were detected with the help of Smatch: drivers/char/ipmi/ipmi_msghandler.c:1381 ipmi_set_my_address() warn: potential spectre issue 'user->intf->addrinfo' [w] (local cap) drivers/char/ipmi/ipmi_msghandler.c:1401 ipmi_get_my_address() warn: potential spectre issue 'user->intf->addrinfo' [r] (local cap) drivers/char/ipmi/ipmi_msghandler.c:1421 ipmi_set_my_LUN() warn: potential spectre issue 'user->intf->addrinfo' [w] (local cap) drivers/char/ipmi/ipmi_msghandler.c:1441 ipmi_get_my_LUN() warn: potential spectre issue 'user->intf->addrinfo' [r] (local cap) drivers/char/ipmi/ipmi_msghandler.c:2260 check_addr() warn: potential spectre issue 'intf->addrinfo' [r] (local cap) Fix this by sanitizing channel and addr->channel before using them to index user->intf->addrinfo and intf->addrinfo, correspondingly. Notice that given that speculation windows are large, the policy is to kill the speculation on the first load and not worry if it can be completed with a dependent load/store [1]. [1] https://lore.kernel.org/lkml/20180423164740.GY17484@dhcp22.suse.cz/ Cc: stable@vger.kernel.org Signed-off-by: Gustavo A. R. Silva Signed-off-by: Corey Minyard --- drivers/char/ipmi/ipmi_msghandler.c | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-) diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c index a74ce885b541..7a9fbe60a840 100644 --- a/drivers/char/ipmi/ipmi_msghandler.c +++ b/drivers/char/ipmi/ipmi_msghandler.c @@ -32,6 +32,7 @@ #include #include #include +#include #define IPMI_DRIVER_VERSION "39.2" @@ -1298,10 +1299,12 @@ int ipmi_set_my_address(struct ipmi_user *user, if (!user) return -ENODEV; - if (channel >= IPMI_MAX_CHANNELS) + if (channel >= IPMI_MAX_CHANNELS) { rv = -EINVAL; - else + } else { + channel = array_index_nospec(channel, IPMI_MAX_CHANNELS); user->intf->addrinfo[channel].address = address; + } release_ipmi_user(user, index); return rv; @@ -1318,10 +1321,12 @@ int ipmi_get_my_address(struct ipmi_user *user, if (!user) return -ENODEV; - if (channel >= IPMI_MAX_CHANNELS) + if (channel >= IPMI_MAX_CHANNELS) { rv = -EINVAL; - else + } else { + channel = array_index_nospec(channel, IPMI_MAX_CHANNELS); *address = user->intf->addrinfo[channel].address; + } release_ipmi_user(user, index); return rv; @@ -1338,10 +1343,12 @@ int ipmi_set_my_LUN(struct ipmi_user *user, if (!user) return -ENODEV; - if (channel >= IPMI_MAX_CHANNELS) + if (channel >= IPMI_MAX_CHANNELS) { rv = -EINVAL; - else + } else { + channel = array_index_nospec(channel, IPMI_MAX_CHANNELS); user->intf->addrinfo[channel].lun = LUN & 0x3; + } release_ipmi_user(user, index); return rv; @@ -1358,10 +1365,12 @@ int ipmi_get_my_LUN(struct ipmi_user *user, if (!user) return -ENODEV; - if (channel >= IPMI_MAX_CHANNELS) + if (channel >= IPMI_MAX_CHANNELS) { rv = -EINVAL; - else + } else { + channel = array_index_nospec(channel, IPMI_MAX_CHANNELS); *address = user->intf->addrinfo[channel].lun; + } release_ipmi_user(user, index); return rv; @@ -2184,6 +2193,7 @@ static int check_addr(struct ipmi_smi *intf, { if (addr->channel >= IPMI_MAX_CHANNELS) return -EINVAL; + addr->channel = array_index_nospec(addr->channel, IPMI_MAX_CHANNELS); *lun = intf->addrinfo[addr->channel].lun; *saddr = intf->addrinfo[addr->channel].address; return 0; From 479d6b39b9e0d2de648ebf146f23a1e40962068f Mon Sep 17 00:00:00 2001 From: Fred Klassen Date: Sat, 19 Jan 2019 14:28:18 -0800 Subject: [PATCH 3/5] ipmi: Prevent use-after-free in deliver_response Some IPMI modules (e.g. ibmpex_msg_handler()) will have ipmi_usr_hdlr handlers that call ipmi_free_recv_msg() directly. This will essentially kfree(msg), leading to use-after-free. This does not happen in the ipmi_devintf module, which will queue the message and run ipmi_free_recv_msg() later. BUG: KASAN: use-after-free in deliver_response+0x12f/0x1b0 Read of size 8 at addr ffff888a7bf20018 by task ksoftirqd/3/27 CPU: 3 PID: 27 Comm: ksoftirqd/3 Tainted: G O 4.19.11-amd64-ani99-debug #12.0.1.601133+pv Hardware name: AppNeta r1000/X11SPW-TF, BIOS 2.1a-AP 09/17/2018 Call Trace: dump_stack+0x92/0xeb print_address_description+0x73/0x290 kasan_report+0x258/0x380 deliver_response+0x12f/0x1b0 ? ipmi_free_recv_msg+0x50/0x50 deliver_local_response+0xe/0x50 handle_one_recv_msg+0x37a/0x21d0 handle_new_recv_msgs+0x1ce/0x440 ... Allocated by task 9885: kasan_kmalloc+0xa0/0xd0 kmem_cache_alloc_trace+0x116/0x290 ipmi_alloc_recv_msg+0x28/0x70 i_ipmi_request+0xb4a/0x1640 ipmi_request_settime+0x1b8/0x1e0 ... Freed by task 27: __kasan_slab_free+0x12e/0x180 kfree+0xe9/0x280 deliver_response+0x122/0x1b0 deliver_local_response+0xe/0x50 handle_one_recv_msg+0x37a/0x21d0 handle_new_recv_msgs+0x1ce/0x440 tasklet_action_common.isra.19+0xc4/0x250 __do_softirq+0x11f/0x51f Fixes: e86ee2d44b44 ("ipmi: Rework locking and shutdown for hot remove") Cc: stable@vger.kernel.org # 4.18 Signed-off-by: Fred Klassen Signed-off-by: Corey Minyard --- drivers/char/ipmi/ipmi_msghandler.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c index 7a9fbe60a840..cc5665c47a0e 100644 --- a/drivers/char/ipmi/ipmi_msghandler.c +++ b/drivers/char/ipmi/ipmi_msghandler.c @@ -885,7 +885,7 @@ static int deliver_response(struct ipmi_smi *intf, struct ipmi_recv_msg *msg) if (user) { user->handler->ipmi_recv_hndl(msg, user->handler_data); - release_ipmi_user(msg->user, index); + release_ipmi_user(user, index); } else { /* User went away, give up. */ ipmi_free_recv_msg(msg); From 77f8269606bf95fcb232ee86f6da80886f1dfae8 Mon Sep 17 00:00:00 2001 From: Yang Yingliang Date: Wed, 16 Jan 2019 13:33:22 +0800 Subject: [PATCH 4/5] ipmi: fix use-after-free of user->release_barrier.rda When we do the following test, we got oops in ipmi_msghandler driver while((1)) do service ipmievd restart & service ipmievd restart done --------------------------------------------------------------- [ 294.230186] Unable to handle kernel paging request at virtual address 0000803fea6ea008 [ 294.230188] Mem abort info: [ 294.230190] ESR = 0x96000004 [ 294.230191] Exception class = DABT (current EL), IL = 32 bits [ 294.230193] SET = 0, FnV = 0 [ 294.230194] EA = 0, S1PTW = 0 [ 294.230195] Data abort info: [ 294.230196] ISV = 0, ISS = 0x00000004 [ 294.230197] CM = 0, WnR = 0 [ 294.230199] user pgtable: 4k pages, 48-bit VAs, pgdp = 00000000a1c1b75a [ 294.230201] [0000803fea6ea008] pgd=0000000000000000 [ 294.230204] Internal error: Oops: 96000004 [#1] SMP [ 294.235211] Modules linked in: nls_utf8 isofs rpcrdma ib_iser ib_srpt target_core_mod ib_srp scsi_transport_srp ib_ipoib rdma_ucm ib_umad rdma_cm ib_cm iw_cm dm_mirror dm_region_hash dm_log dm_mod aes_ce_blk crypto_simd cryptd aes_ce_cipher ghash_ce sha2_ce ses sha256_arm64 sha1_ce hibmc_drm hisi_sas_v2_hw enclosure sg hisi_sas_main sbsa_gwdt ip_tables mlx5_ib ib_uverbs marvell ib_core mlx5_core ixgbe ipmi_si mdio hns_dsaf ipmi_devintf ipmi_msghandler hns_enet_drv hns_mdio [ 294.277745] CPU: 3 PID: 0 Comm: swapper/3 Kdump: loaded Not tainted 5.0.0-rc2+ #113 [ 294.285511] Hardware name: Huawei TaiShan 2280 /BC11SPCD, BIOS 1.37 11/21/2017 [ 294.292835] pstate: 80000005 (Nzcv daif -PAN -UAO) [ 294.297695] pc : __srcu_read_lock+0x38/0x58 [ 294.301940] lr : acquire_ipmi_user+0x2c/0x70 [ipmi_msghandler] [ 294.307853] sp : ffff00001001bc80 [ 294.311208] x29: ffff00001001bc80 x28: ffff0000117e5000 [ 294.316594] x27: 0000000000000000 x26: dead000000000100 [ 294.321980] x25: dead000000000200 x24: ffff803f6bd06800 [ 294.327366] x23: 0000000000000000 x22: 0000000000000000 [ 294.332752] x21: ffff00001001bd04 x20: ffff80df33d19018 [ 294.338137] x19: ffff80df33d19018 x18: 0000000000000000 [ 294.343523] x17: 0000000000000000 x16: 0000000000000000 [ 294.348908] x15: 0000000000000000 x14: 0000000000000002 [ 294.354293] x13: 0000000000000000 x12: 0000000000000000 [ 294.359679] x11: 0000000000000000 x10: 0000000000100000 [ 294.365065] x9 : 0000000000000000 x8 : 0000000000000004 [ 294.370451] x7 : 0000000000000000 x6 : ffff80df34558678 [ 294.375836] x5 : 000000000000000c x4 : 0000000000000000 [ 294.381221] x3 : 0000000000000001 x2 : 0000803fea6ea000 [ 294.386607] x1 : 0000803fea6ea008 x0 : 0000000000000001 [ 294.391994] Process swapper/3 (pid: 0, stack limit = 0x0000000083087293) [ 294.398791] Call trace: [ 294.401266] __srcu_read_lock+0x38/0x58 [ 294.405154] acquire_ipmi_user+0x2c/0x70 [ipmi_msghandler] [ 294.410716] deliver_response+0x80/0xf8 [ipmi_msghandler] [ 294.416189] deliver_local_response+0x28/0x68 [ipmi_msghandler] [ 294.422193] handle_one_recv_msg+0x158/0xcf8 [ipmi_msghandler] [ 294.432050] handle_new_recv_msgs+0xc0/0x210 [ipmi_msghandler] [ 294.441984] smi_recv_tasklet+0x8c/0x158 [ipmi_msghandler] [ 294.451618] tasklet_action_common.isra.5+0x88/0x138 [ 294.460661] tasklet_action+0x2c/0x38 [ 294.468191] __do_softirq+0x120/0x2f8 [ 294.475561] irq_exit+0x134/0x140 [ 294.482445] __handle_domain_irq+0x6c/0xc0 [ 294.489954] gic_handle_irq+0xb8/0x178 [ 294.497037] el1_irq+0xb0/0x140 [ 294.503381] arch_cpu_idle+0x34/0x1a8 [ 294.510096] do_idle+0x1d4/0x290 [ 294.516322] cpu_startup_entry+0x28/0x30 [ 294.523230] secondary_start_kernel+0x184/0x1d0 [ 294.530657] Code: d538d082 d2800023 8b010c81 8b020021 (c85f7c25) [ 294.539746] ---[ end trace 8a7a880dee570b29 ]--- [ 294.547341] Kernel panic - not syncing: Fatal exception in interrupt [ 294.556837] SMP: stopping secondary CPUs [ 294.563996] Kernel Offset: disabled [ 294.570515] CPU features: 0x002,21006008 [ 294.577638] Memory Limit: none [ 294.587178] Starting crashdump kernel... [ 294.594314] Bye! Because the user->release_barrier.rda is freed in ipmi_destroy_user(), but the refcount is not zero, when acquire_ipmi_user() uses user->release_barrier.rda in __srcu_read_lock(), it causes oops. Fix this by calling cleanup_srcu_struct() when the refcount is zero. Fixes: e86ee2d44b44 ("ipmi: Rework locking and shutdown for hot remove") Cc: stable@vger.kernel.org # 4.18 Signed-off-by: Yang Yingliang Signed-off-by: Corey Minyard --- drivers/char/ipmi/ipmi_msghandler.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c index cc5665c47a0e..e43c27ff59b4 100644 --- a/drivers/char/ipmi/ipmi_msghandler.c +++ b/drivers/char/ipmi/ipmi_msghandler.c @@ -1184,6 +1184,7 @@ EXPORT_SYMBOL(ipmi_get_smi_info); static void free_user(struct kref *ref) { struct ipmi_user *user = container_of(ref, struct ipmi_user, refcount); + cleanup_srcu_struct(&user->release_barrier); kfree(user); } @@ -1260,7 +1261,6 @@ int ipmi_destroy_user(struct ipmi_user *user) { _ipmi_destroy_user(user); - cleanup_srcu_struct(&user->release_barrier); kref_put(&user->refcount, free_user); return 0; From 913a89f009d98c85a902d718cd54bb32ab11d167 Mon Sep 17 00:00:00 2001 From: Corey Minyard Date: Thu, 20 Dec 2018 16:50:23 -0600 Subject: [PATCH 5/5] ipmi: Don't initialize anything in the core until something uses it The IPMI driver was recently modified to use SRCU, but it turns out this uses a chunk of percpu memory, even if IPMI is never used. So modify thing to on initialize on the first use. There was already code to sort of handle this for handling init races, so piggy back on top of that, and simplify it in the process. Signed-off-by: Corey Minyard Reported-by: Tejun Heo Cc: Paul E. McKenney Reviewed-by: Paul E. McKenney Cc: stable@vger.kernel.org # 4.18 --- drivers/char/ipmi/ipmi_msghandler.c | 143 ++++++++++++++++------------ 1 file changed, 80 insertions(+), 63 deletions(-) diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c index e43c27ff59b4..c518659b4d9f 100644 --- a/drivers/char/ipmi/ipmi_msghandler.c +++ b/drivers/char/ipmi/ipmi_msghandler.c @@ -63,7 +63,8 @@ static void ipmi_debug_msg(const char *title, unsigned char *data, { } #endif -static int initialized; +static bool initialized; +static bool drvregistered; enum ipmi_panic_event_op { IPMI_SEND_PANIC_EVENT_NONE, @@ -613,7 +614,7 @@ static DEFINE_MUTEX(ipmidriver_mutex); static LIST_HEAD(ipmi_interfaces); static DEFINE_MUTEX(ipmi_interfaces_mutex); -DEFINE_STATIC_SRCU(ipmi_interfaces_srcu); +struct srcu_struct ipmi_interfaces_srcu; /* * List of watchers that want to know when smi's are added and deleted. @@ -721,7 +722,15 @@ struct watcher_entry { int ipmi_smi_watcher_register(struct ipmi_smi_watcher *watcher) { struct ipmi_smi *intf; - int index; + int index, rv; + + /* + * Make sure the driver is actually initialized, this handles + * problems with initialization order. + */ + rv = ipmi_init_msghandler(); + if (rv) + return rv; mutex_lock(&smi_watchers_mutex); @@ -1077,7 +1086,7 @@ int ipmi_create_user(unsigned int if_num, { unsigned long flags; struct ipmi_user *new_user; - int rv = 0, index; + int rv, index; struct ipmi_smi *intf; /* @@ -1095,18 +1104,9 @@ int ipmi_create_user(unsigned int if_num, * Make sure the driver is actually initialized, this handles * problems with initialization order. */ - if (!initialized) { - rv = ipmi_init_msghandler(); - if (rv) - return rv; - - /* - * The init code doesn't return an error if it was turned - * off, but it won't initialize. Check that. - */ - if (!initialized) - return -ENODEV; - } + rv = ipmi_init_msghandler(); + if (rv) + return rv; new_user = kmalloc(sizeof(*new_user), GFP_KERNEL); if (!new_user) @@ -3301,17 +3301,9 @@ int ipmi_register_smi(const struct ipmi_smi_handlers *handlers, * Make sure the driver is actually initialized, this handles * problems with initialization order. */ - if (!initialized) { - rv = ipmi_init_msghandler(); - if (rv) - return rv; - /* - * The init code doesn't return an error if it was turned - * off, but it won't initialize. Check that. - */ - if (!initialized) - return -ENODEV; - } + rv = ipmi_init_msghandler(); + if (rv) + return rv; intf = kzalloc(sizeof(*intf), GFP_KERNEL); if (!intf) @@ -5027,6 +5019,22 @@ static int panic_event(struct notifier_block *this, return NOTIFY_DONE; } +/* Must be called with ipmi_interfaces_mutex held. */ +static int ipmi_register_driver(void) +{ + int rv; + + if (drvregistered) + return 0; + + rv = driver_register(&ipmidriver.driver); + if (rv) + pr_err("Could not register IPMI driver\n"); + else + drvregistered = true; + return rv; +} + static struct notifier_block panic_block = { .notifier_call = panic_event, .next = NULL, @@ -5037,66 +5045,75 @@ static int ipmi_init_msghandler(void) { int rv; + mutex_lock(&ipmi_interfaces_mutex); + rv = ipmi_register_driver(); + if (rv) + goto out; if (initialized) - return 0; + goto out; - rv = driver_register(&ipmidriver.driver); - if (rv) { - pr_err("Could not register IPMI driver\n"); - return rv; - } - - pr_info("version " IPMI_DRIVER_VERSION "\n"); + init_srcu_struct(&ipmi_interfaces_srcu); timer_setup(&ipmi_timer, ipmi_timeout, 0); mod_timer(&ipmi_timer, jiffies + IPMI_TIMEOUT_JIFFIES); atomic_notifier_chain_register(&panic_notifier_list, &panic_block); - initialized = 1; + initialized = true; - return 0; +out: + mutex_unlock(&ipmi_interfaces_mutex); + return rv; } static int __init ipmi_init_msghandler_mod(void) { - ipmi_init_msghandler(); - return 0; + int rv; + + pr_info("version " IPMI_DRIVER_VERSION "\n"); + + mutex_lock(&ipmi_interfaces_mutex); + rv = ipmi_register_driver(); + mutex_unlock(&ipmi_interfaces_mutex); + + return rv; } static void __exit cleanup_ipmi(void) { int count; - if (!initialized) - return; + if (initialized) { + atomic_notifier_chain_unregister(&panic_notifier_list, + &panic_block); - atomic_notifier_chain_unregister(&panic_notifier_list, &panic_block); + /* + * This can't be called if any interfaces exist, so no worry + * about shutting down the interfaces. + */ - /* - * This can't be called if any interfaces exist, so no worry - * about shutting down the interfaces. - */ + /* + * Tell the timer to stop, then wait for it to stop. This + * avoids problems with race conditions removing the timer + * here. + */ + atomic_inc(&stop_operation); + del_timer_sync(&ipmi_timer); - /* - * Tell the timer to stop, then wait for it to stop. This - * avoids problems with race conditions removing the timer - * here. - */ - atomic_inc(&stop_operation); - del_timer_sync(&ipmi_timer); + initialized = false; - driver_unregister(&ipmidriver.driver); + /* Check for buffer leaks. */ + count = atomic_read(&smi_msg_inuse_count); + if (count != 0) + pr_warn("SMI message count %d at exit\n", count); + count = atomic_read(&recv_msg_inuse_count); + if (count != 0) + pr_warn("recv message count %d at exit\n", count); - initialized = 0; - - /* Check for buffer leaks. */ - count = atomic_read(&smi_msg_inuse_count); - if (count != 0) - pr_warn("SMI message count %d at exit\n", count); - count = atomic_read(&recv_msg_inuse_count); - if (count != 0) - pr_warn("recv message count %d at exit\n", count); + cleanup_srcu_struct(&ipmi_interfaces_srcu); + } + if (drvregistered) + driver_unregister(&ipmidriver.driver); } module_exit(cleanup_ipmi);