[PATCH RFC] nvme: fix NS head cdev lifetime
John Garry <[email protected]>
| Newsgroups | org.infradead.lists.linux-nvme |
|---|---|
| Message-ID | <[email protected]> |
Sashiko bot reported a potential problem for the NS head cdev lifetime in the libmultipath refactoring in [0]. Currently the NS head .open and .release file_operations methods take a reference to the nvme_ns_head to ensure that this structure does not disappear while we have files open. When we teardown the NS head, we call nvme_cdev_del() -> cdev_device_del() -> cdev_del(). However after cdev_del() returns, cdevs already open will remain and their fops will still be callable. As such, we can still reference the cdev after the nvme_ns_head reference count drops to 0 (and is freed). This can be shown with an application which delays between opening the cdev and issuing the ioctl while the NS head is being torn down: # ./ioctl_file /dev/ng1n1 & # waiting 10 seconds .... # ./ini_nvme_teardown.sh [ 21.221718] nvme nvme1: Removing ctrl: NQN "nvme-test-target" [ 21.274609] nvme nvme2: Removing ctrl: NQN "nvme-test-target" # now going to issue ioctl .... [ 26.549285] ================================================================== [ 26.550841] BUG: KASAN: slab-use-after-free in cdev_put.part.0+0x3d/0x40 [ 26.552352] Read of size 8 at addr ffff88811e7fa170 by task ioctl_file/237 [ 26.553805] [ 26.554227] CPU: 3 UID: 0 PID: 237 Comm: ioctl_file Not tainted 7.2.0-rc1-00004-g6852a10e32d4 #921 PREEMPT(lazy) [ 26.554236] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 1.16.3-debian-1.16.3-2 04/01/2014 [ 26.554241] Call Trace: [ 26.554245] <TASK> [ 26.554248] dump_stack_lvl+0x68/0xa0 [ 26.554266] print_report+0x10d/0x5d0 [ 26.554276] ? __virt_addr_valid+0x21d/0x3f0 [ 26.554287] ? cdev_put.part.0+0x3d/0x40 [ 26.554292] kasan_report+0x96/0xd0 [ 26.554300] ? cdev_put.part.0+0x3d/0x40 [ 26.554307] cdev_put.part.0+0x3d/0x40 [ 26.554313] __fput+0x7bc/0xa70 [ 26.554322] fput_close_sync+0xd8/0x190 [ 26.554328] ? __pfx_fput_close_sync+0x10/0x10 [ 26.554337] __x64_sys_close+0x79/0xd0 [ 26.554344] do_syscall_64+0x117/0x6b0 [ 26.554351] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 26.554358] RIP: 0033:0x7f938c067727 [ 26.554364] Code: 48 89 fa 4c 89 df e8 28 ad 00 00 8b 93 08 03 00 00 59 5e 48 83 f8 fc 74 1a 5b c3 0f 1f 84 00 00 00 00 00 48 8b 44 24 10 0f 05 <5bf [ 26.554369] RSP: 002b:00007fff49f05980 EFLAGS: 00000202 ORIG_RAX: 0000000000000003 [ 26.554376] RAX: ffffffffffffffda RBX: 00007f938bfd7780 RCX: 00007f938c067727 [ 26.554380] RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003 [ 26.554383] RBP: 00007fff49f05a10 R08: 0000000000000000 R09: 0000000000000000 [ 26.554386] R10: 0000000000000000 R11: 0000000000000202 R12: 0000000000000000 [ 26.554389] R13: 00007fff49f05b40 R14: 00007f938c207000 R15: 000055c148471d78 [ 26.554397] </TASK> [ 26.554399] [ 26.575612] Allocated by task 100: [ 26.575871] kasan_save_stack+0x24/0x50 [ 26.576157] kasan_save_track+0x14/0x30 [ 26.576418] __kasan_kmalloc+0x7f/0x90 [ 26.576668] __kmalloc_noprof+0x281/0x6c0 [ 26.576938] nvme_alloc_ns+0x7f7/0x3170 [ 26.577206] nvme_scan_ns+0x508/0x880 [ 26.577449] async_run_entry_fn+0x8c/0x350 [ 26.577723] process_scheduled_works+0xb6f/0x1a00 [ 26.578034] worker_thread+0x4ad/0xb40 [ 26.578283] kthread+0x34f/0x450 [ 26.578501] ret_from_fork+0x563/0x800 [ 26.578752] ret_from_fork_asm+0x1a/0x30 [ 26.579012] [ 26.579124] Freed by task 237: [ 26.579335] kasan_save_stack+0x24/0x50 [ 26.579596] kasan_save_track+0x14/0x30 [ 26.579855] kasan_save_free_info+0x3a/0x60 [ 26.580131] __kasan_slab_free+0x43/0x70 [ 26.580388] kfree+0x321/0x500 [ 26.580591] nvme_ns_head_chr_release+0x39/0x50 [ 26.580883] __fput+0x352/0xa70 [ 26.581095] fput_close_sync+0xd8/0x190 [ 26.581350] __x64_sys_close+0x79/0xd0 [ 26.581595] do_syscall_64+0x117/0x6b0 [ 26.581842] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 26.582176] [ 26.582286] Last potentially related work creation: [ 26.582593] kasan_save_stack+0x24/0x50 [ 26.582841] kasan_record_aux_stack+0x89/0xa0 [ 26.583210] insert_work+0x22/0x170 [ 26.583442] __queue_work+0x7b1/0xfa0 [ 26.583682] queue_work_on+0x77/0x80 [ 26.583921] kblockd_schedule_work+0x18/0x20 [ 26.584207] nvme_mpath_put_disk+0x42/0xa0 [ 26.584632] nvme_free_ns_head+0x1c/0x160 [ 26.584904] nvme_ns_head_chr_release+0x39/0x50 [ 26.585208] __fput+0x352/0xa70 [ 26.585420] fput_close_sync+0xd8/0x190 [ 26.585677] __x64_sys_close+0x79/0xd0 [ 26.585924] do_syscall_64+0x117/0x6b0 [ 26.586173] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 26.586505] [ 26.586616] Second to last potentially related work creation: [ 26.586991] kasan_save_stack+0x24/0x50 [ 26.587246] kasan_record_aux_stack+0x89/0xa0 [ 26.587538] insert_work+0x22/0x170 [ 26.587770] __queue_work+0x7b1/0xfa0 [ 26.588010] queue_work_on+0x77/0x80 [ 26.588247] kblockd_schedule_work+0x18/0x20 [ 26.588529] nvme_remove_head+0x3d/0xb0 [ 26.588787] nvme_ns_remove+0x4b2/0x930 [ 26.589040] nvme_remove_namespaces+0x29c/0x410 [ 26.589340] nvme_do_delete_ctrl+0xf3/0x190 [ 26.589611] nvme_delete_ctrl_sync+0x71/0x90 [ 26.589889] nvme_sysfs_delete+0x91/0xb0 [ 26.590151] kernfs_fop_write_iter+0x2fb/0x4a0 [ 26.590452] vfs_write+0x929/0xfc0 [ 26.590688] ksys_write+0xf2/0x1d0 [ 26.590923] do_syscall_64+0x117/0x6b0 [ 26.591171] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 26.591498] [ 26.591605] The buggy address belongs to the object at ffff88811e7fa000 [ 26.591605] which belongs to the cache kmalloc-4k of size 4096 [ 26.592409] The buggy address is located 368 bytes inside of [ 26.592409] freed 4096-byte region [ffff88811e7fa000, ffff88811e7fb000) [ 26.593205] [ 26.593321] The buggy address belongs to the physical page: [ 26.593701] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x11e7f8 [ 26.594250] head: order:3 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0 [ 26.594743] flags: 0x200000000000040(head|node=0|zone=2) [ 26.595093] page_type: f5(slab) [ 26.595312] raw: 0200000000000040 ffff888100043040 dead000000000122 0000000000000000 [ 26.595810] raw: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000 [ 26.596309] head: 0200000000000040 ffff888100043040 dead000000000122 0000000000000000 [ 26.596806] head: 0000000000000000 0000000000040004 00000000f5000000 0000000000000000 [ 26.597313] head: 0200000000000003 fffffffffffffe01 00000000ffffffff 00000000ffffffff [ 26.597813] head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000 [ 26.598317] page dumped because: kasan: bad access detected [ 26.598676] [ 26.598784] Memory state around the buggy address: [ 26.599093] ffff88811e7fa000: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 26.599559] ffff88811e7fa080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 26.600023] >ffff88811e7fa100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 26.600485] ^ [ 26.600921] ffff88811e7fa180: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 26.601390] ffff88811e7fa200: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb [ 26.601855] ================================================================== [ 26.602374] Disabling lock debugging due to kernel taint When all fds for the cdev disappear, the cdev removal path puts a reference to the parent object, which is the nvme_ns_head.cdev_device - see cdev_default_release() -> kobject_put(parent). We can use the lifetime of the cdev_device to resolve this lifetime issue. Fix the lifetime for the cdev by making adding the cdev add take a reference to the NS head and drop that reference in the nvme_ns_head.cdev_device release function. [0] https://lore.kernel.org/linux-scsi/[email protected]/T/#m67265e2906d617acd2743c0a00809246d0cfc506 Signed-off-by: John Garry <[email protected]> --- Setting as RFC as I am not sure if this is the best solution. diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index 453c1f0b2dd09..c7578b7ed6b76 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -3887,7 +3887,7 @@ static int nvme_subsys_check_duplicate_ids(struct nvme_subsystem *subsys, return 0; } -static void nvme_cdev_rel(struct device *dev) +void nvme_cdev_rel(struct device *dev) { ida_free(&nvme_ns_chr_minor_ida, MINOR(dev->devt)); } @@ -3900,7 +3900,8 @@ void nvme_cdev_del(struct cdev *cdev, struct device *cdev_device) int nvme_cdev_add(const char *name, struct cdev *cdev, struct device *cdev_device, - const struct file_operations *fops, struct module *owner) + const struct file_operations *fops, struct module *owner, + void (*release)(struct device *cdev_dev)) { int minor, ret; @@ -3915,7 +3916,7 @@ int nvme_cdev_add(const char *name, struct cdev *cdev, } cdev_device->devt = MKDEV(MAJOR(nvme_ns_chr_devt), minor); cdev_device->class = &nvme_ns_chr_class; - cdev_device->release = nvme_cdev_rel; + cdev_device->release = release; device_initialize(cdev_device); cdev_init(cdev, fops); cdev->owner = owner; @@ -3956,7 +3957,8 @@ static void nvme_add_ns_cdev(struct nvme_ns *ns) ns->head->instance); if (nvme_cdev_add(name, &ns->cdev, &ns->cdev_device, - &nvme_ns_chr_fops, ns->ctrl->ops->module)) { + &nvme_ns_chr_fops, ns->ctrl->ops->module, + nvme_cdev_rel)) { dev_err(ns->ctrl->device, "Unable to create the %s device\n", name); return; diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c index 9b9a657fa330f..016b6b0128c71 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -616,29 +616,23 @@ static inline struct nvme_ns_head *cdev_to_ns_head(struct cdev *cdev) return container_of(cdev, struct nvme_ns_head, cdev); } -static int nvme_ns_head_chr_open(struct inode *inode, struct file *file) -{ - if (!nvme_tryget_ns_head(cdev_to_ns_head(inode->i_cdev))) - return -ENXIO; - return 0; -} - -static int nvme_ns_head_chr_release(struct inode *inode, struct file *file) -{ - nvme_put_ns_head(cdev_to_ns_head(inode->i_cdev)); - return 0; -} - static const struct file_operations nvme_ns_head_chr_fops = { .owner = THIS_MODULE, - .open = nvme_ns_head_chr_open, - .release = nvme_ns_head_chr_release, .unlocked_ioctl = nvme_ns_head_chr_ioctl, .compat_ioctl = compat_ptr_ioctl, .uring_cmd = nvme_ns_head_chr_uring_cmd, .uring_cmd_iopoll = nvme_ns_chr_uring_cmd_iopoll, }; +static void nvme_cdev_ns_head_rel(struct device *dev) +{ + struct nvme_ns_head *head = container_of(dev, struct nvme_ns_head, + cdev_device); + + nvme_cdev_rel(dev); + nvme_put_ns_head(head); +} + static void nvme_add_ns_head_cdev(struct nvme_ns_head *head) { char name[32]; @@ -647,11 +641,15 @@ static void nvme_add_ns_head_cdev(struct nvme_ns_head *head) snprintf(name, sizeof(name), "ng%dn%d", head->subsys->instance, head->instance); - if (nvme_cdev_add(name, &head->cdev, &head->cdev_device, - &nvme_ns_head_chr_fops, THIS_MODULE)) { - dev_err(disk_to_dev(head->disk), - "Unable to create the %s device\n", name); - return; + if (nvme_tryget_ns_head(head)) { + if (nvme_cdev_add(name, &head->cdev, &head->cdev_device, + &nvme_ns_head_chr_fops, THIS_MODULE, + nvme_cdev_ns_head_rel)) { + dev_err(disk_to_dev(head->disk), + "Unable to create the %s device\n", name); + nvme_put_ns_head(head); + return; + } } set_bit(NVME_NSHEAD_CDEV_LIVE, &head->flags); } diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h index 824651cc898db..60d2d35926743 100644 --- a/drivers/nvme/host/nvme.h +++ b/drivers/nvme/host/nvme.h @@ -999,8 +999,10 @@ bool nvme_tryget_ns_head(struct nvme_ns_head *head); void nvme_put_ns_head(struct nvme_ns_head *head); int nvme_cdev_add(const char *name, struct cdev *cdev, struct device *cdev_device, - const struct file_operations *fops, struct module *owner); + const struct file_operations *fops, struct module *owner, + void (*release)(struct device *cdev_device)); void nvme_cdev_del(struct cdev *cdev, struct device *cdev_device); +void nvme_cdev_rel(struct device *dev); int nvme_ioctl(struct block_device *bdev, blk_mode_t mode, unsigned int cmd, unsigned long arg); long nvme_ns_chr_ioctl(struct file *file, unsigned int cmd, unsigned long arg); -- 2.43.7