Messages in this thread Patch in this message | | | From | Duoming Zhou <> | Subject | [PATCH net v4] nfc: nfcmrvl: main: reorder destructive operations in nfcmrvl_nci_unregister_dev to avoid bugs | Date | Wed, 27 Apr 2022 09:14:38 +0800 |
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There are destructive operations such as nfcmrvl_fw_dnld_abort and gpio_free in nfcmrvl_nci_unregister_dev. The resources such as firmware, gpio and so on could be destructed while the upper layer functions such as nfcmrvl_fw_dnld_start and nfcmrvl_nci_recv_frame is executing, which leads to double-free, use-after-free and null-ptr-deref bugs.
There are three situations that could lead to double-free bugs.
The first situation is shown below:
(Thread 1) | (Thread 2) nfcmrvl_fw_dnld_start | ... | nfcmrvl_nci_unregister_dev release_firmware() | nfcmrvl_fw_dnld_abort kfree(fw) //(1) | fw_dnld_over | release_firmware ... | kfree(fw) //(2) | ...
The second situation is shown below:
(Thread 1) | (Thread 2) nfcmrvl_fw_dnld_start | ... | mod_timer | (wait a time) | fw_dnld_timeout | nfcmrvl_nci_unregister_dev fw_dnld_over | nfcmrvl_fw_dnld_abort release_firmware | fw_dnld_over kfree(fw) //(1) | release_firmware ... | kfree(fw) //(2)
The third situation is shown below:
(Thread 1) | (Thread 2) nfcmrvl_nci_recv_frame | if(..->fw_download_in_progress)| nfcmrvl_fw_dnld_recv_frame | queue_work | | fw_dnld_rx_work | nfcmrvl_nci_unregister_dev fw_dnld_over | nfcmrvl_fw_dnld_abort release_firmware | fw_dnld_over kfree(fw) //(1) | release_firmware | kfree(fw) //(2)
The firmware struct is deallocated in position (1) and deallocated in position (2) again.
The crash trace triggered by POC is like below:
[ 122.640457] BUG: KASAN: double-free or invalid-free in fw_dnld_over+0x28/0xf0 [ 122.640457] Call Trace: [ 122.640457] <TASK> [ 122.640457] kfree+0xb0/0x330 [ 122.640457] fw_dnld_over+0x28/0xf0 [ 122.640457] nfcmrvl_nci_unregister_dev+0x61/0x70 [ 122.640457] nci_uart_tty_close+0x87/0xd0 [ 122.640457] tty_ldisc_kill+0x3e/0x80 [ 122.640457] tty_ldisc_hangup+0x1b2/0x2c0 [ 122.640457] __tty_hangup.part.0+0x316/0x520 [ 122.640457] tty_release+0x200/0x670 [ 122.640457] __fput+0x110/0x410 [ 122.640457] task_work_run+0x86/0xd0 [ 122.640457] exit_to_user_mode_prepare+0x1aa/0x1b0 [ 122.640457] syscall_exit_to_user_mode+0x19/0x50 [ 122.640457] do_syscall_64+0x48/0x90 [ 122.640457] entry_SYSCALL_64_after_hwframe+0x44/0xae [ 122.640457] RIP: 0033:0x7f68433f6beb
What's more, there are also use-after-free and null-ptr-deref bugs in nfcmrvl_fw_dnld_start. If we deallocate firmware struct, gpio or set null to the members of priv->fw_dnld in nfcmrvl_nci_unregister_dev, then, we dereference firmware, gpio or the members of priv->fw_dnld in nfcmrvl_fw_dnld_start, the UAF or NPD bugs will happen.
This patch reorders destructive operations after nci_unregister_device and adds bool variable protected by device_lock to synchronize between cleanup routine and firmware download routine. The process is shown below.
(Thread 1) | (Thread 2) nfcmrvl_nci_unregister_dev | nci_unregister_device | nfc_unregister_device | nfc_fw_download device_lock() | ... | nfc_download = false; | ... device_unlock() | ... | device_lock() (destructive operations) | if(.. || !nfc_download) | goto error; | error: | device_unlock()
If the device is detaching, the download function will goto error. If the download function is executing, nci_unregister_device will wait until download function is finished.
Fixes: 3194c6870158 ("NFC: nfcmrvl: add firmware download support") Signed-off-by: Duoming Zhou <duoming@zju.edu.cn> --- Changes in v4: - Change bool variable nfc_download to static.
drivers/nfc/nfcmrvl/main.c | 2 +- net/nfc/core.c | 6 +++++- 2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/drivers/nfc/nfcmrvl/main.c b/drivers/nfc/nfcmrvl/main.c index 2fcf545012b..1a5284de434 100644 --- a/drivers/nfc/nfcmrvl/main.c +++ b/drivers/nfc/nfcmrvl/main.c @@ -183,6 +183,7 @@ void nfcmrvl_nci_unregister_dev(struct nfcmrvl_private *priv) { struct nci_dev *ndev = priv->ndev; + nci_unregister_device(ndev); if (priv->ndev->nfc_dev->fw_download_in_progress) nfcmrvl_fw_dnld_abort(priv); @@ -191,7 +192,6 @@ void nfcmrvl_nci_unregister_dev(struct nfcmrvl_private *priv) if (gpio_is_valid(priv->config.reset_n_io)) gpio_free(priv->config.reset_n_io); - nci_unregister_device(ndev); nci_free_device(ndev); kfree(priv); } diff --git a/net/nfc/core.c b/net/nfc/core.c index dc7a2404efd..1d91334ee86 100644 --- a/net/nfc/core.c +++ b/net/nfc/core.c @@ -25,6 +25,8 @@ #define NFC_CHECK_PRES_FREQ_MS 2000 int nfc_devlist_generation; +/* nfc_download: used to judge whether nfc firmware download could start */ +static bool nfc_download; DEFINE_MUTEX(nfc_devlist_mutex); /* NFC device ID bitmap */ @@ -38,7 +40,7 @@ int nfc_fw_download(struct nfc_dev *dev, const char *firmware_name) device_lock(&dev->dev); - if (!device_is_registered(&dev->dev)) { + if (!device_is_registered(&dev->dev) || !nfc_download) { rc = -ENODEV; goto error; } @@ -1134,6 +1136,7 @@ int nfc_register_device(struct nfc_dev *dev) dev->rfkill = NULL; } } + nfc_download = true; device_unlock(&dev->dev); rc = nfc_genl_device_added(dev); @@ -1166,6 +1169,7 @@ void nfc_unregister_device(struct nfc_dev *dev) rfkill_unregister(dev->rfkill); rfkill_destroy(dev->rfkill); } + nfc_download = false; device_unlock(&dev->dev); if (dev->ops->check_presence) { -- 2.17.1
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