pinmux: Use sequential access to access desc->pinmux data

Vulnerability Description

In the Linux kernel, the following vulnerability has been resolved: pinmux: Use sequential access to access desc->pinmux data When two client of the same gpio call pinctrl_select_state() for the same functionality, we are seeing NULL pointer issue while accessing desc->mux_owner. Let's say two processes A, B executing in pin_request() for the same pin and process A updates the desc->mux_usecount but not yet updated the desc->mux_owner while process B see the desc->mux_usecount which got updated by A path and further executes strcmp and while accessing desc->mux_owner it crashes with NULL pointer. Serialize the access to mux related setting with a mutex lock. cpu0 (process A) cpu1(process B) pinctrl_select_state() { pinctrl_select_state() { pin_request() { pin_request() { ... .... } else { desc->mux_usecount++; desc->mux_usecount && strcmp(desc->mux_owner, owner)) { if (desc->mux_usecount > 1) return 0; desc->mux_owner = owner; } }

References

• https://git.kernel.org/stable/c/2da32aed4a97ca1d70fb8b77926f72f30ce5fb4b
• https://git.kernel.org/stable/c/c11e2ec9a780f54982a187ee10ffd1b810715c85
• https://git.kernel.org/stable/c/5a3e85c3c397c781393ea5fb2f45b1f60f8a4e6e