CVE-2024-50046 in Linux
Summary
by MITRE • 10/21/2024
In the Linux kernel, the following vulnerability has been resolved:
NFSv4: Prevent NULL-pointer dereference in nfs42_complete_copies()
On the node of an NFS client, some files saved in the mountpoint of the NFS server were copied to another location of the same NFS server. Accidentally, the nfs42_complete_copies() got a NULL-pointer dereference crash with the following syslog:
[232064.838881] NFSv4: state recovery failed for open file nfs/pvc-12b5200d-cd0f-46a3-b9f0-af8f4fe0ef64.qcow2, error = -116
[232064.839360] NFSv4: state recovery failed for open file nfs/pvc-12b5200d-cd0f-46a3-b9f0-af8f4fe0ef64.qcow2, error = -116
[232066.588183] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000058
[232066.588586] Mem abort info:
[232066.588701] ESR = 0x0000000096000007
[232066.588862] EC = 0x25: DABT (current EL), IL = 32 bits
[232066.589084] SET = 0, FnV = 0
[232066.589216] EA = 0, S1PTW = 0
[232066.589340] FSC = 0x07: level 3 translation fault
[232066.589559] Data abort info:
[232066.589683] ISV = 0, ISS = 0x00000007
[232066.589842] CM = 0, WnR = 0
[232066.589967] user pgtable: 64k pages, 48-bit VAs, pgdp=00002000956ff400
[232066.590231] [0000000000000058] pgd=08001100ae100003, p4d=08001100ae100003, pud=08001100ae100003, pmd=08001100b3c00003, pte=0000000000000000
[232066.590757] Internal error: Oops: 96000007 [#1] SMP
[232066.590958] Modules linked in: rpcsec_gss_krb5 auth_rpcgss nfsv4 dns_resolver nfs lockd grace fscache netfs ocfs2_dlmfs ocfs2_stack_o2cb ocfs2_dlm vhost_net vhost vhost_iotlb tap tun ipt_rpfilter xt_multiport ip_set_hash_ip ip_set_hash_net xfrm_interface xfrm6_tunnel tunnel4 tunnel6 esp4 ah4 wireguard libcurve25519_generic veth xt_addrtype xt_set nf_conntrack_netlink ip_set_hash_ipportnet ip_set_hash_ipportip ip_set_bitmap_port ip_set_hash_ipport dummy ip_set ip_vs_sh ip_vs_wrr ip_vs_rr ip_vs iptable_filter sch_ingress nfnetlink_cttimeout vport_gre ip_gre ip_tunnel gre vport_geneve geneve vport_vxlan vxlan ip6_udp_tunnel udp_tunnel openvswitch nf_conncount dm_round_robin dm_service_time dm_multipath xt_nat xt_MASQUERADE nft_chain_nat nf_nat xt_mark xt_conntrack xt_comment nft_compat nft_counter nf_tables nfnetlink ocfs2 ocfs2_nodemanager ocfs2_stackglue iscsi_tcp libiscsi_tcp libiscsi scsi_transport_iscsi ipmi_ssif nbd overlay 8021q garp mrp bonding tls rfkill sunrpc ext4 mbcache jbd2
[232066.591052] vfat fat cas_cache cas_disk ses enclosure scsi_transport_sas sg acpi_ipmi ipmi_si ipmi_devintf ipmi_msghandler ip_tables vfio_pci vfio_pci_core vfio_virqfd vfio_iommu_type1 vfio dm_mirror dm_region_hash dm_log dm_mod nf_conntrack nf_defrag_ipv6 nf_defrag_ipv4 br_netfilter bridge stp llc fuse xfs libcrc32c ast drm_vram_helper qla2xxx drm_kms_helper syscopyarea crct10dif_ce sysfillrect ghash_ce sysimgblt sha2_ce fb_sys_fops cec sha256_arm64 sha1_ce drm_ttm_helper ttm nvme_fc igb sbsa_gwdt nvme_fabrics drm nvme_core i2c_algo_bit i40e scsi_transport_fc megaraid_sas aes_neon_bs
[232066.596953] CPU: 6 PID: 4124696 Comm: 10.253.166.125- Kdump: loaded Not tainted 5.15.131-9.cl9_ocfs2.aarch64 #1
[232066.597356] Hardware name: Great Wall .\x93\x8e...RF6260 V5/GWMSSE2GL1T, BIOS T656FBE_V3.0.18 2024-01-06
[232066.597721] pstate: 20400009 (nzCv daif +PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[232066.598034] pc : nfs4_reclaim_open_state+0x220/0x800 [nfsv4]
[232066.598327] lr : nfs4_reclaim_open_state+0x12c/0x800 [nfsv4]
[232066.598595] sp : ffff8000f568fc70
[232066.598731] x29: ffff8000f568fc70 x28: 0000000000001000 x27: ffff21003db33000
[232066.599030] x26: ffff800005521ae0 x25: ffff0100f98fa3f0 x24: 0000000000000001
[232066.599319] x23: ffff800009920008 x22: ffff21003db33040 x21: ffff21003db33050
[232066.599628] x20: ffff410172fe9e40 x19: ffff410172fe9e00 x18: 0000000000000000
[232066.599914] x17: 0000000000000000 x16: 0000000000000004 x15: 0000000000000000
[232066.600195] x14: 0000000000000000 x13: ffff800008e685a8 x12: 00000000eac0c6e6
[232066.600498] x11: 00000000000000
---truncated---
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Analysis
by VulDB Data Team • 03/23/2026
The vulnerability CVE-2024-50046 represents a critical NULL-pointer dereference flaw within the Linux kernel's NFSv4 implementation, specifically in the nfs42_complete_copies() function. This issue arises during the handling of file copy operations between locations on the same NFS server, where the kernel fails to properly validate pointer references, leading to an immediate system crash. The flaw manifests when the kernel attempts to access a memory address that has not been properly initialized or allocated, resulting in an unhandled kernel NULL pointer dereference at virtual address 0x58. The crash occurs during state recovery operations for open files, as evidenced by the syslog entries indicating failures in NFSv4 state recovery for specific qcow2 files, followed by the kernel oops and memory abort information.
The technical root cause of this vulnerability lies in improper validation of data structures within the NFSv4 state management code, particularly when processing copy operations in NFS version 4.2. The kernel's nfs42_complete_copies() function does not adequately check for NULL pointers before dereferencing them, which violates fundamental security principles of memory safety. This behavior aligns with CWE-476, which describes NULL pointer dereference vulnerabilities, and represents a classic example of insufficient input validation in kernel space. The crash occurs in the context of nfs4_reclaim_open_state function, suggesting that the issue is triggered during recovery operations when the kernel attempts to reestablish file state after a network disruption or server restart, indicating that this vulnerability can be exploited during normal NFS operations but is more likely to manifest under stress conditions or after network interruptions.
From an operational perspective, this vulnerability presents a significant risk to systems relying on NFSv4 for storage operations, particularly in virtualized environments where qcow2 disk images are commonly used. The crash results in immediate system instability and potential data loss, as the kernel panics and terminates the NFS client operations. The impact extends beyond simple service disruption, as the vulnerability can be leveraged to cause denial of service attacks against NFS clients, potentially affecting entire storage clusters or virtual machine environments. The vulnerability's exploitation is facilitated by normal NFS operations, making it particularly dangerous in production environments where NFS is heavily utilized for persistent storage. According to ATT&CK framework, this vulnerability maps to T1499.004 (Authorization Scripting and Libraries) and T1566.002 (Phishing via Service) as it can be used to create persistent denial of service conditions and potentially as part of broader attack chains targeting storage infrastructure. The specific memory access pattern and the use of aarch64 architecture in the crash report suggests that the vulnerability may be more prevalent in ARM-based systems, though similar issues could exist on other architectures.
Mitigation strategies for CVE-2024-50046 should focus on immediate kernel updates to address the NULL-pointer dereference in the nfs42_complete_copies() function, as provided in the latest kernel security patches. System administrators should prioritize patching affected NFS clients, particularly those running kernel versions prior to the fix, and monitor for any signs of system instability or crashes during NFS operations. Additional mitigations include implementing network monitoring to detect unusual NFS state recovery patterns and configuring automatic failover mechanisms to minimize service disruption. Organizations should also consider temporarily disabling NFSv4 copy operations until patches are deployed, and implement comprehensive logging to track NFS client operations that may trigger the vulnerability. The fix typically involves adding proper NULL pointer checks before dereferencing pointers in the nfs42_complete_copies() function, which aligns with standard secure coding practices and defensive programming principles. Given the nature of the vulnerability, regular security audits of NFS configurations and kernel versions should be conducted to ensure all systems remain protected against similar issues.