Bug 2425196 (CVE-2023-54114)

Summary: CVE-2023-54114 kernel: Linux kernel: Denial of Service due to incorrect network packet processing in NSH module
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: low    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel, specifically within its Network Service Header (NSH) module. A local attacker could exploit this vulnerability by sending specially crafted network packets, which would cause the system to crash. This issue, a type of Denial of Service (DoS), arises from an incorrect calculation during network packet processing, leading to a critical error in memory management.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2025-12-24 14:10:07 UTC
In the Linux kernel, the following vulnerability has been resolved:

net: nsh: Use correct mac_offset to unwind gso skb in nsh_gso_segment()

As the call trace shows, skb_panic was caused by wrong skb->mac_header
in nsh_gso_segment():

invalid opcode: 0000 [#1] PREEMPT SMP KASAN PTI
CPU: 3 PID: 2737 Comm: syz Not tainted 6.3.0-next-20230505 #1
RIP: 0010:skb_panic+0xda/0xe0
call Trace:
 skb_push+0x91/0xa0
 nsh_gso_segment+0x4f3/0x570
 skb_mac_gso_segment+0x19e/0x270
 __skb_gso_segment+0x1e8/0x3c0
 validate_xmit_skb+0x452/0x890
 validate_xmit_skb_list+0x99/0xd0
 sch_direct_xmit+0x294/0x7c0
 __dev_queue_xmit+0x16f0/0x1d70
 packet_xmit+0x185/0x210
 packet_snd+0xc15/0x1170
 packet_sendmsg+0x7b/0xa0
 sock_sendmsg+0x14f/0x160

The root cause is:
nsh_gso_segment() use skb->network_header - nhoff to reset mac_header
in skb_gso_error_unwind() if inner-layer protocol gso fails.
However, skb->network_header may be reset by inner-layer protocol
gso function e.g. mpls_gso_segment. skb->mac_header reset by the
inaccurate network_header will be larger than skb headroom.

nsh_gso_segment
    nhoff = skb->network_header - skb->mac_header;
    __skb_pull(skb,nsh_len)
    skb_mac_gso_segment
        mpls_gso_segment
            skb_reset_network_header(skb);//skb->network_header+=nsh_len
            return -EINVAL;
    skb_gso_error_unwind
        skb_push(skb, nsh_len);
        skb->mac_header = skb->network_header - nhoff;
        // skb->mac_header > skb->headroom, cause skb_push panic

Use correct mac_offset to restore mac_header and get rid of nhoff.