CVE-2023-52598

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> s390/ptrace: handle setting of fpc register correctly<br /> <br /> If the content of the floating point control (fpc) register of a traced<br /> process is modified with the ptrace interface the new value is tested for<br /> validity by temporarily loading it into the fpc register.<br /> <br /> This may lead to corruption of the fpc register of the tracing process:<br /> if an interrupt happens while the value is temporarily loaded into the<br /> fpc register, and within interrupt context floating point or vector<br /> registers are used, the current fp/vx registers are saved with<br /> save_fpu_regs() assuming they belong to user space and will be loaded into<br /> fp/vx registers when returning to user space.<br /> <br /> test_fp_ctl() restores the original user space fpc register value, however<br /> it will be discarded, when returning to user space.<br /> <br /> In result the tracer will incorrectly continue to run with the value that<br /> was supposed to be used for the traced process.<br /> <br /> Fix this by saving fpu register contents with save_fpu_regs() before using<br /> test_fp_ctl().