CVE-2026-31624HID: core: clamp report_size in s32ton() to avoid undefined shift

Official description

In the Linux kernel, the following vulnerability has been resolved: HID: core: clamp report_size in s32ton() to avoid undefined shift s32ton() shifts by n-1 where n is the field's report_size, a value that comes directly from a HID device. The HID parser bounds report_size only to <= 256, so a broken HID device can supply a report descriptor with a wide field that triggers shift exponents up to 256 on a 32-bit type when an output report is built via hid_output_field() or hid_set_field(). Commit ec61b41918587 ("HID: core: fix shift-out-of-bounds in hid_report_raw_event") added the same n > 32 clamp to the function snto32(), but s32ton() was never given the same fix as I guess syzbot hadn't figured out how to fuzz a device the same way. Fix this up by just clamping the max value of n, just like snto32() does.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/76ad02854a30c394e0c076e6e6bed0a388573a94
• https://git.kernel.org/stable/c/eb415ddaf25e09ddb8fe5736a70c9de2e6462534
• https://git.kernel.org/stable/c/0ab048dbdb1daacf17d52e9252297eb6e1298e49
• https://git.kernel.org/stable/c/932ae5309e53561197aa7d1606c7cf63af10e24f
• https://git.kernel.org/stable/c/58386f00af710922cafb0fb69211497beddfaa95
• https://git.kernel.org/stable/c/8a8333237f1f5caab8d4c3d2c2e7578c4263a97f
• https://git.kernel.org/stable/c/ea363a34086ddb4231adc581a7f36c39ec154bfc
• https://git.kernel.org/stable/c/97014719bb8fccb1ffcbbc299e84b1f11b114195
• https://git.kernel.org/stable/c/69c02ffde6ed4d535fa4e693a9e572729cad3d0d
• https://cert-portal.siemens.com/productcert/html/ssa-784472.html