CVE-2021-47413

In the Linux kernel, the following vulnerability has been resolved:

usb: chipidea: ci_hdrc_imx: Also search for phys phandle

When passing phys in the devicetree to describe the USB PHY phandle (which is the recommended way according to Documentation/devicetree/bindings/usb/ci-hdrc-usb2.txt) the following NULL pointer dereference is observed on i.MX7 and i.MX8MM:

[ 1.489344] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000098 [ 1.498170] Mem abort info: [ 1.500966] ESR = 0x96000044 [ 1.504030] EC = 0x25: DABT (current EL), IL = 32 bits [ 1.509356] SET = 0, FnV = 0 [ 1.512416] EA = 0, S1PTW = 0 [ 1.515569] FSC = 0x04: level 0 translation fault [ 1.520458] Data abort info: [ 1.523349] ISV = 0, ISS = 0x00000044 [ 1.527196] CM = 0, WnR = 1 [ 1.530176] [0000000000000098] user address but active_mm is swapper [ 1.536544] Internal error: Oops: 96000044 [#1] PREEMPT SMP [ 1.542125] Modules linked in: [ 1.545190] CPU: 3 PID: 7 Comm: kworker/u8:0 Not tainted 5.14.0-dirty #3 [ 1.551901] Hardware name: Kontron i.MX8MM N801X S (DT) [ 1.557133] Workqueue: events_unbound deferred_probe_work_func [ 1.562984] pstate: 80000005 (Nzcv daif -PAN -UAO -TCO BTYPE=–) [ 1.568998] pc : imx7d_charger_detection+0x3f0/0x510 [ 1.573973] lr : imx7d_charger_detection+0x22c/0x510

This happens because the charger functions check for the phy presence inside the imx_usbmisc_data structure (data->usb_phy), but the chipidea core populates the usb_phy passed via phys inside struct ci_hdrc (ci->usb_phy) instead.

This causes the NULL pointer dereference inside imx7d_charger_detection().

Fix it by also searching for phys in case fsl,usbphy is not found.

Tested on a imx7s-warp board.

Weakness

The product dereferences a pointer that it expects to be valid but is NULL.

Affected Software

Potential Mitigations

References

• https://git.kernel.org/stable/c/66dd03b10e1c0b2fae006c6e34c18ea8ee033e7b
• https://git.kernel.org/stable/c/8253a34bfae3278baca52fc1209b7c29270486ca
• https://git.kernel.org/stable/c/b3265b88e83b16c7be762fa5fb7e0632bce0002c
• https://git.kernel.org/stable/c/66dd03b10e1c0b2fae006c6e34c18ea8ee033e7b
• https://git.kernel.org/stable/c/8253a34bfae3278baca52fc1209b7c29270486ca
• https://git.kernel.org/stable/c/b3265b88e83b16c7be762fa5fb7e0632bce0002c