In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conntrack_h323: Add protection for bmp length out of range UBSAN load reports an exception of BRK#5515 SHIFT_ISSUE:Bitwise shifts that are out of bounds for their data type. vmlinux get_bitmap(b=75) + 712 vmlinux decode_seq(bs=0xFFFFFFD008037000, f=0xFFFFFFD008037018, level=134443100) + 1956 vmlinux decode_choice(base=0xFFFFFFD0080370F0, level=23843636) + 1216 vmlinux decode_seq(f=0xFFFFFFD0080371A8, level=134443500) + 812 vmlinux decode_choice(base=0xFFFFFFD008037280, level=0) + 1216 vmlinux DecodeRasMessage() + 304 vmlinux ras_help() + 684 vmlinux nf_confirm() + 188 Due to abnormal data in skb->data, the extension bitmap length exceeds 32 when decoding ras message then uses the length to make a shift operation. It will change into negative after several loop. UBSAN load could detect a negative shift as an undefined behaviour and reports exception. So we add the protection to avoid the length exceeding 32. Or else it will return out of range error and stop decoding.