CVE-2025-38556: 
Linux Kernel vulnerability analysis and mitigation

CVE-2025-38556 is a vulnerability discovered in the Linux kernel's HID core component. The issue was identified when testing by the syzbot fuzzer revealed a shift-out-of-bounds exception occurring during the conversion of a 32-bit quantity to a 0-bit quantity in the s32ton() function (NVD).

The vulnerability manifests when the HID core attempts to process a report field with size set to zero, leading to a shift-out-of-bounds exception in the s32ton() function. While this scenario should ideally never occur, the presence of buggy devices makes it a practical concern. The issue requires hardening of the s32ton() routine to handle zero-bit conversions gracefully, similar to the behavior of snto32() (NVD).

When exploited, this vulnerability could cause the system to crash due to the shift-out-of-bounds exception. While the direct impact appears to be limited to denial of service through system crashes, the vulnerability affects the core HID functionality of the Linux kernel (NVD).

The vulnerability has been addressed by hardening the s32ton() routine to return a reasonable result instead of crashing when called with zero bits, matching the behavior of snto32(). This fix has been implemented in the Linux kernel (NVD).