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.