Vulnerability CVE-2024-26851

Vulnerability CVE-2024-26851

Published: 2024-04-17

Description:

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
<net/netfilter/nf_conntrack_h323_asn1.c:0>
vmlinux decode_seq(bs=0xFFFFFFD008037000, f=0xFFFFFFD008037018, level=134443100) + 1956
<net/netfilter/nf_conntrack_h323_asn1.c:592>
vmlinux decode_choice(base=0xFFFFFFD0080370F0, level=23843636) + 1216
<net/netfilter/nf_conntrack_h323_asn1.c:814>
vmlinux decode_seq(f=0xFFFFFFD0080371A8, level=134443500) + 812
<net/netfilter/nf_conntrack_h323_asn1.c:576>
vmlinux decode_choice(base=0xFFFFFFD008037280, level=0) + 1216
<net/netfilter/nf_conntrack_h323_asn1.c:814>
vmlinux DecodeRasMessage() + 304
<net/netfilter/nf_conntrack_h323_asn1.c:833>
vmlinux ras_help() + 684
<net/netfilter/nf_conntrack_h323_main.c:1728>
vmlinux nf_confirm() + 188
<net/netfilter/nf_conntrack_proto.c:137>

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.

References:

https://git.kernel.org/stable/c/98db42191329c679f4ca52bec0b319689e1ad8cb

https://git.kernel.org/stable/c/4bafcc43baf7bcf93566394dbd15726b5b456b7a

https://git.kernel.org/stable/c/ccd1108b16ab572d9bf635586b0925635dbd6bbc

https://git.kernel.org/stable/c/b3c0f553820516ad4b62a9390ecd28d6f73a7b13

https://git.kernel.org/stable/c/39001e3c42000e7c2038717af0d33c32319ad591

https://git.kernel.org/stable/c/014a807f1cc9c9d5173c1cd935835553b00d211c

https://git.kernel.org/stable/c/80ee5054435a11c87c9a4f30f1ff750080c96416

https://git.kernel.org/stable/c/767146637efc528b5e3d31297df115e85a2fd362

Copyright 2024, cxsecurity.com