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    Subject[PATCH 4.19 016/243] NFC: nxp-nci: Fix NULL pointer dereference after I2C communication error
    Date
    From: Stephan Gerhold <stephan@gerhold.net>

    [ 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
    irq_thread_fn+0x20/0x60
    irq_thread+0xee/0x180
    ? wake_threads_waitq+0x30/0x30
    kthread+0xfb/0x130
    ? irq_thread_check_affinity+0xd0/0xd0
    ? kthread_park+0x90/0x90
    ret_from_fork+0x1f/0x40

    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@gerhold.net>
    Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Sasha Levin <sashal@kernel.org>
    ---
    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 ba695e392c3b7..0df745cad601a 100644
    --- a/drivers/nfc/nxp-nci/i2c.c
    +++ b/drivers/nfc/nxp-nci/i2c.c
    @@ -236,8 +236,10 @@ 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;
    }
    --
    2.20.1


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