CVE-2021-47631

/// Technical description

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

ARM: davinci: da850-evm: Avoid NULL pointer dereference

With newer versions of GCC, there is a panic in da850_evm_config_emac()

when booting multi_v5_defconfig in QEMU under the palmetto-bmc machine:

Unable to handle kernel NULL pointer dereference at virtual address 00000020

pgd = (ptrval)

[00000020] *pgd=00000000

Internal error: Oops: 5 [#1] PREEMPT ARM

Modules linked in:

CPU: 0 PID: 1 Comm: swapper Not tainted 5.15.0 #1

Hardware name: Generic DT based system

PC is at da850_evm_config_emac+0x1c/0x120

LR is at do_one_initcall+0x50/0x1e0

The emac_pdata pointer in soc_info is NULL because davinci_soc_info only

gets populated on davinci machines but da850_evm_config_emac() is called

on all machines via device_initcall().

Move the rmii_en assignment below the machine check so that it is only

dereferenced when running on a supported SoC.

/// Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

/// References