memory: tegra20-emc: fix an OF node reference bug in tegra_emc_find_node_by_ram_code()

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: memory: tegra20-emc: fix an OF node reference bug in tegra_emc_find_node_by_ram_code() As of_find_node_by_name() release the reference of the argument device node, tegra_emc_find_node_by_ram_code() releases some device nodes while still in use, resulting in possible UAFs. According to the bindings and the in-tree DTS files, the "emc-tables" node is always device's child node with the property "nvidia,use-ram-code", and the "lpddr2" node is a child of the "emc-tables" node. Thus utilize the for_each_child_of_node() macro and of_get_child_by_name() instead of of_find_node_by_name() to simplify the code. This bug was found by an experimental verification tool that I am developing. [krzysztof: applied v1, adjust the commit msg to incorporate v2 parts]

References

• https://git.kernel.org/stable/c/c3def10c610ae046aaa61d00528e7bd15e4ad8d3
• https://git.kernel.org/stable/c/e9d07e91de140679eeaf275f47ad154467cb9e05
• https://git.kernel.org/stable/c/c144423cb07e4e227a8572d5742ca2b36ada770d
• https://git.kernel.org/stable/c/3b02273446e23961d910b50cc12528faec649fb2
• https://git.kernel.org/stable/c/755e44538c190c31de9090d8e8821d228fcfd416
• https://git.kernel.org/stable/c/b9784e5cde1f9fb83661a70e580e381ae1264d12