linux-dev/net/nfc/nci/core.c, branch linus/master

nfc: nci: add flush_workqueue to prevent uaf

2022-04-13T13:44:44Z

Our detector found a concurrent use-after-free bug when detaching an NCI device. The main reason for this bug is the unexpected scheduling between the used delayed mechanism (timer and workqueue). The race can be demonstrated below: Thread-1 Thread-2 | nci_dev_up() | nci_open_device() | __nci_request(nci_reset_req) | nci_send_cmd | queue_work(cmd_work) nci_unregister_device() | nci_close_device() | ... del_timer_sync(cmd_timer)[1] | ... | Worker nci_free_device() | nci_cmd_work() kfree(ndev)[3] | mod_timer(cmd_timer)[2] In short, the cleanup routine thought that the cmd_timer has already been detached by [1] but the mod_timer can re-attach the timer [2], even it is already released [3], resulting in UAF. This UAF is easy to trigger, crash trace by POC is like below [ 66.703713] ================================================================== [ 66.703974] BUG: KASAN: use-after-free in enqueue_timer+0x448/0x490 [ 66.703974] Write of size 8 at addr ffff888009fb7058 by task kworker/u4:1/33 [ 66.703974] [ 66.703974] CPU: 1 PID: 33 Comm: kworker/u4:1 Not tainted 5.18.0-rc2 #5 [ 66.703974] Workqueue: nfc2_nci_cmd_wq nci_cmd_work [ 66.703974] Call Trace: [ 66.703974] [ 66.703974] dump_stack_lvl+0x57/0x7d [ 66.703974] print_report.cold+0x5e/0x5db [ 66.703974] ? enqueue_timer+0x448/0x490 [ 66.703974] kasan_report+0xbe/0x1c0 [ 66.703974] ? enqueue_timer+0x448/0x490 [ 66.703974] enqueue_timer+0x448/0x490 [ 66.703974] __mod_timer+0x5e6/0xb80 [ 66.703974] ? mark_held_locks+0x9e/0xe0 [ 66.703974] ? try_to_del_timer_sync+0xf0/0xf0 [ 66.703974] ? lockdep_hardirqs_on_prepare+0x17b/0x410 [ 66.703974] ? queue_work_on+0x61/0x80 [ 66.703974] ? lockdep_hardirqs_on+0xbf/0x130 [ 66.703974] process_one_work+0x8bb/0x1510 [ 66.703974] ? lockdep_hardirqs_on_prepare+0x410/0x410 [ 66.703974] ? pwq_dec_nr_in_flight+0x230/0x230 [ 66.703974] ? rwlock_bug.part.0+0x90/0x90 [ 66.703974] ? _raw_spin_lock_irq+0x41/0x50 [ 66.703974] worker_thread+0x575/0x1190 [ 66.703974] ? process_one_work+0x1510/0x1510 [ 66.703974] kthread+0x2a0/0x340 [ 66.703974] ? kthread_complete_and_exit+0x20/0x20 [ 66.703974] ret_from_fork+0x22/0x30 [ 66.703974] [ 66.703974] [ 66.703974] Allocated by task 267: [ 66.703974] kasan_save_stack+0x1e/0x40 [ 66.703974] __kasan_kmalloc+0x81/0xa0 [ 66.703974] nci_allocate_device+0xd3/0x390 [ 66.703974] nfcmrvl_nci_register_dev+0x183/0x2c0 [ 66.703974] nfcmrvl_nci_uart_open+0xf2/0x1dd [ 66.703974] nci_uart_tty_ioctl+0x2c3/0x4a0 [ 66.703974] tty_ioctl+0x764/0x1310 [ 66.703974] __x64_sys_ioctl+0x122/0x190 [ 66.703974] do_syscall_64+0x3b/0x90 [ 66.703974] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 66.703974] [ 66.703974] Freed by task 406: [ 66.703974] kasan_save_stack+0x1e/0x40 [ 66.703974] kasan_set_track+0x21/0x30 [ 66.703974] kasan_set_free_info+0x20/0x30 [ 66.703974] __kasan_slab_free+0x108/0x170 [ 66.703974] kfree+0xb0/0x330 [ 66.703974] nfcmrvl_nci_unregister_dev+0x90/0xd0 [ 66.703974] nci_uart_tty_close+0xdf/0x180 [ 66.703974] tty_ldisc_kill+0x73/0x110 [ 66.703974] tty_ldisc_hangup+0x281/0x5b0 [ 66.703974] __tty_hangup.part.0+0x431/0x890 [ 66.703974] tty_release+0x3a8/0xc80 [ 66.703974] __fput+0x1f0/0x8c0 [ 66.703974] task_work_run+0xc9/0x170 [ 66.703974] exit_to_user_mode_prepare+0x194/0x1a0 [ 66.703974] syscall_exit_to_user_mode+0x19/0x50 [ 66.703974] do_syscall_64+0x48/0x90 [ 66.703974] entry_SYSCALL_64_after_hwframe+0x44/0xae To fix the UAF, this patch adds flush_workqueue() to ensure the nci_cmd_work is finished before the following del_timer_sync. This combination will promise the timer is actually detached. Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation") Signed-off-by: Lin Ma Reviewed-by: Krzysztof Kozlowski Signed-off-by: David S. Miller

NFC: add NCI_UNREG flag to eliminate the race

2021-11-18T04:17:05Z

There are two sites that calls queue_work() after the destroy_workqueue() and lead to possible UAF. The first site is nci_send_cmd(), which can happen after the nci_close_device as below nfcmrvl_nci_unregister_dev | nfc_genl_dev_up nci_close_device | flush_workqueue | del_timer_sync | nci_unregister_device | nfc_get_device destroy_workqueue | nfc_dev_up nfc_unregister_device | nci_dev_up device_del | nci_open_device | __nci_request | nci_send_cmd | queue_work !!! Another site is nci_cmd_timer, awaked by the nci_cmd_work from the nci_send_cmd. ... | ... nci_unregister_device | queue_work destroy_workqueue | nfc_unregister_device | ... device_del | nci_cmd_work | mod_timer | ... | nci_cmd_timer | queue_work !!! For the above two UAF, the root cause is that the nfc_dev_up can race between the nci_unregister_device routine. Therefore, this patch introduce NCI_UNREG flag to easily eliminate the possible race. In addition, the mutex_lock in nci_close_device can act as a barrier. Signed-off-by: Lin Ma Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation") Reviewed-by: Jakub Kicinski Reviewed-by: Krzysztof Kozlowski Link: https://lore.kernel.org/r/20211116152732.19238-1-linma@zju.edu.cn Signed-off-by: Jakub Kicinski

NFC: reorganize the functions in nci_request

2021-11-18T04:16:53Z

There is a possible data race as shown below: thread-A in nci_request() | thread-B in nci_close_device() | mutex_lock(&ndev->req_lock); test_bit(NCI_UP, &ndev->flags); | ... | test_and_clear_bit(NCI_UP, &ndev->flags) mutex_lock(&ndev->req_lock); | | This race will allow __nci_request() to be awaked while the device is getting removed. Similar to commit e2cb6b891ad2 ("bluetooth: eliminate the potential race condition when removing the HCI controller"). this patch alters the function sequence in nci_request() to prevent the data races between the nci_close_device(). Signed-off-by: Lin Ma Fixes: 6a2968aaf50c ("NFC: basic NCI protocol implementation") Link: https://lore.kernel.org/r/20211115145600.8320-1-linma@zju.edu.cn Signed-off-by: Jakub Kicinski

nfc: drop unneeded debug prints

2021-10-12T00:00:51Z

ftrace is a preferred and standard way to debug entering and exiting functions so drop useless debug prints. Signed-off-by: Krzysztof Kozlowski Signed-off-by: Jakub Kicinski

nfc: hci: pass callback data param as pointer in nci_request()

2021-08-02T14:11:37Z

The nci_request() receives a callback function and unsigned long data argument "opt" which is passed to the callback. Almost all of the nci_request() callers pass pointer to a stack variable as data argument. Only few pass scalar value (e.g. u8). All such callbacks do not modify passed data argument and in previous commit they were made as const. However passing pointers via unsigned long removes the const annotation. The callback could simply cast unsigned long to a pointer to writeable memory. Use "const void *" as type of this "opt" argument to solve this and prevent modifying the pointed contents. This is also consistent with generic pattern of passing data arguments - via "void *". In few places which pass scalar values, use casts via "unsigned long" to suppress any warnings. Signed-off-by: Krzysztof Kozlowski Signed-off-by: David S. Miller

nfc: hci: cleanup unneeded spaces

2021-07-30T15:22:53Z

No need for multiple spaces in variable declaration (the code does not use them in other places). No functional change. Signed-off-by: Krzysztof Kozlowski Signed-off-by: Jakub Kicinski

nfc: nci: constify several pointers to u8, sk_buff and other structs

2021-07-30T15:22:52Z

Several functions receive pointers to u8, sk_buff or other structs but do not modify the contents so make them const. This allows doing the same for local variables and in total makes the code a little bit safer. This makes const also data passed as "unsigned long opt" argument to nci_request() function. Usual flow for such functions is: 1. Receive "u8 *" and store it (the pointer) in a structure allocated on stack (e.g. struct nci_set_config_param), 2. Call nci_request() or __nci_request() passing a callback function an the pointer to the structure via an "unsigned long opt", 3. nci_request() calls the callback which dereferences "unsigned long opt" in a read-only way. This converts all above paths to use proper pointer to const data, so entire flow is safer. Signed-off-by: Krzysztof Kozlowski Signed-off-by: Jakub Kicinski

nfc: constify nfc_ops

2021-07-25T08:21:21Z

Neither the core nor the drivers modify the passed pointer to struct nfc_ops, so make it a pointer to const for correctness and safety. Signed-off-by: Krzysztof Kozlowski Signed-off-by: David S. Miller

nfc: constify nci_driver_ops (prop_ops and core_ops)

2021-07-25T08:21:21Z

Neither the core nor the drivers modify the passed pointer to struct nci_driver_ops (consisting of function pointers), so make it a pointer to const for correctness and safety. Signed-off-by: Krzysztof Kozlowski Signed-off-by: David S. Miller

nfc: constify nci_ops

2021-07-25T08:21:20Z

The struct nci_ops is modified by NFC core in only one case: nci_allocate_device() receives too many proprietary commands (prop_ops) to configure. This is a build time known constrain, so a graceful handling of such case is not necessary. Instead, fail the nci_allocate_device() and add BUILD_BUG_ON() to places which set these. This allows to constify the struct nci_ops (consisting of function pointers) for correctness and safety. Signed-off-by: Krzysztof Kozlowski Signed-off-by: David S. Miller