[PATCH 5.3 025/105] NFC: nxp-nci: Fix NULL pointer dereference after I2C communication error

From: Greg Kroah-Hartman
Date: Wed Dec 11 2019 - 10:12:14 EST

From: Stephan Gerhold <stephan@xxxxxxxxxxx>

[ Upstream commit a71a29f50de1ef97ab55c151a1598eb12dde379d ]

I2C communication errors (-EREMOTEIO) during the IRQ handler of nxp-nci
result in a NULL pointer dereference at the moment:

BUG: kernel NULL pointer dereference, address: 0000000000000000
Oops: 0002 [#1] PREEMPT SMP NOPTI
CPU: 1 PID: 355 Comm: irq/137-nxp-nci Not tainted 5.4.0-rc6 #1
RIP: 0010:skb_queue_tail+0x25/0x50
Call Trace:
nci_recv_frame+0x36/0x90 [nci]
nxp_nci_i2c_irq_thread_fn+0xd1/0x285 [nxp_nci_i2c]
? preempt_count_add+0x68/0xa0
? irq_forced_thread_fn+0x80/0x80
? wake_threads_waitq+0x30/0x30
? irq_thread_check_affinity+0xd0/0xd0
? kthread_park+0x90/0x90

Afterward the kernel must be rebooted to work properly again.

This happens because it attempts to call nci_recv_frame() with skb == NULL.
However, unlike nxp_nci_fw_recv_frame(), nci_recv_frame() does not have any
NULL checks for skb, causing the NULL pointer dereference.

Change the code to call only nxp_nci_fw_recv_frame() in case of an error.
Make sure to log it so it is obvious that a communication error occurred.
The error above then becomes:

nxp-nci_i2c i2c-NXP1001:00: NFC: Read failed with error -121
nci: __nci_request: wait_for_completion_interruptible_timeout failed 0
nxp-nci_i2c i2c-NXP1001:00: NFC: Read failed with error -121

Fixes: 6be88670fc59 ("NFC: nxp-nci_i2c: Add I2C support to NXP NCI driver")
Signed-off-by: Stephan Gerhold <stephan@xxxxxxxxxxx>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
drivers/nfc/nxp-nci/i2c.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/nfc/nxp-nci/i2c.c b/drivers/nfc/nxp-nci/i2c.c
index 4aeb3861b4095..6c468899f2ffe 100644
--- a/drivers/nfc/nxp-nci/i2c.c
+++ b/drivers/nfc/nxp-nci/i2c.c
@@ -225,8 +225,10 @@ static irqreturn_t nxp_nci_i2c_irq_thread_fn(int irq, void *phy_id)

if (r == -EREMOTEIO) {
phy->hard_fault = r;
- skb = NULL;
- } else if (r < 0) {
+ if (info->mode == NXP_NCI_MODE_FW)
+ nxp_nci_fw_recv_frame(phy->ndev, NULL);
+ }
+ if (r < 0) {
nfc_err(&client->dev, "Read failed with error %d\n", r);
goto exit_irq_handled;