CVE-2024-46785 in Linux
Summary
by MITRE • 09/18/2024
In the Linux kernel, the following vulnerability has been resolved:
eventfs: Use list_del_rcu() for SRCU protected list variable
Chi Zhiling reported:
We found a null pointer accessing in tracefs[1], the reason is that the
variable 'ei_child' is set to LIST_POISON1, that means the list was removed in eventfs_remove_rec. so when access the ei_child->is_freed, the panic triggered.
by the way, the following script can reproduce this panic
loop1 (){
while true do echo "p:kp submit_bio" > /sys/kernel/debug/tracing/kprobe_events echo "" > /sys/kernel/debug/tracing/kprobe_events done } loop2 (){
while true do tree /sys/kernel/debug/tracing/events/kprobes/ done } loop1 & loop2
[1]:
[ 1147.959632][T17331] Unable to handle kernel paging request at virtual address dead000000000150
[ 1147.968239][T17331] Mem abort info:
[ 1147.971739][T17331] ESR = 0x0000000096000004
[ 1147.976172][T17331] EC = 0x25: DABT (current EL), IL = 32 bits
[ 1147.982171][T17331] SET = 0, FnV = 0
[ 1147.985906][T17331] EA = 0, S1PTW = 0
[ 1147.989734][T17331] FSC = 0x04: level 0 translation fault
[ 1147.995292][T17331] Data abort info:
[ 1147.998858][T17331] ISV = 0, ISS = 0x00000004, ISS2 = 0x00000000
[ 1148.005023][T17331] CM = 0, WnR = 0, TnD = 0, TagAccess = 0
[ 1148.010759][T17331] GCS = 0, Overlay = 0, DirtyBit = 0, Xs = 0
[ 1148.016752][T17331] [dead000000000150] address between user and kernel address ranges
[ 1148.024571][T17331] Internal error: Oops: 0000000096000004 [#1] SMP
[ 1148.030825][T17331] Modules linked in: team_mode_loadbalance team nlmon act_gact cls_flower sch_ingress bonding tls macvlan dummy ib_core bridge stp llc veth amdgpu amdxcp mfd_core gpu_sched drm_exec drm_buddy radeon crct10dif_ce video drm_suballoc_helper ghash_ce drm_ttm_helper sha2_ce ttm sha256_arm64 i2c_algo_bit sha1_ce sbsa_gwdt cp210x drm_display_helper cec sr_mod cdrom drm_kms_helper binfmt_misc sg loop fuse drm dm_mod nfnetlink ip_tables autofs4 [last unloaded: tls]
[ 1148.072808][T17331] CPU: 3 PID: 17331 Comm: ls Tainted: G W ------- ---- 6.6.43 #2
[ 1148.081751][T17331] Source Version: 21b3b386e948bedd29369af66f3e98ab01b1c650
[ 1148.088783][T17331] Hardware name: Greatwall GW-001M1A-FTF/GW-001M1A-FTF, BIOS KunLun BIOS V4.0 07/16/2020
[ 1148.098419][T17331] pstate: 20000005 (nzCv daif -PAN -UAO -TCO -DIT -SSBS BTYPE=--)
[ 1148.106060][T17331] pc : eventfs_iterate+0x2c0/0x398
[ 1148.111017][T17331] lr : eventfs_iterate+0x2fc/0x398
[ 1148.115969][T17331] sp : ffff80008d56bbd0
[ 1148.119964][T17331] x29: ffff80008d56bbf0 x28: ffff001ff5be2600 x27: 0000000000000000
[ 1148.127781][T17331] x26: ffff001ff52ca4e0 x25: 0000000000009977 x24: dead000000000100
[ 1148.135598][T17331] x23: 0000000000000000 x22: 000000000000000b x21: ffff800082645f10
[ 1148.143415][T17331] x20: ffff001fddf87c70 x19: ffff80008d56bc90 x18: 0000000000000000
[ 1148.151231][T17331] x17: 0000000000000000 x16: 0000000000000000 x15: ffff001ff52ca4e0
[ 1148.159048][T17331] x14: 0000000000000000 x13: 0000000000000000 x12: 0000000000000000
[ 1148.166864][T17331] x11: 0000000000000000 x10: 0000000000000000 x9 : ffff8000804391d0
[ 1148.174680][T17331] x8 : 0000000180000000 x7 : 0000000000000018 x6 : 0000aaab04b92862
[ 1148.182498][T17331] x5 : 0000aaab04b92862 x4 : 0000000080000000 x3 : 0000000000000068
[ 1148.190314][T17331] x2 : 000000000000000f x1 : 0000000000007ea8 x0 : 0000000000000001
[ 1148.198131][T17331] Call trace:
[ 1148.201259][T17331] eventfs_iterate+0x2c0/0x398
[ 1148.205864][T17331] iterate_dir+0x98/0x188
[ 1148.210036][T17331] __arm64_sys_getdents64+0x78/0x160
[ 1148.215161][T17331] invoke_syscall+0x78/0x108
[ 1148.219593][T17331] el0_svc_common.constprop.0+0x48/0xf0
[ 1148.224977][T17331] do_el0_svc+0x24/0x38
[ 1148.228974][T17331] el0_svc+0x40/0x168
[ 1148.232798][T17
---truncated---
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Analysis
by VulDB Data Team • 04/06/2026
The vulnerability described in CVE-2024-46785 resides within the Linux kernel's eventfs subsystem, specifically concerning the improper handling of list operations in a SRCU-protected data structure. This flaw manifests as a race condition that can lead to a kernel panic due to a null pointer dereference when accessing a list node that has already been removed. The issue is particularly concerning because it involves concurrent access patterns where one thread removes an element from a list while another thread attempts to traverse or access that same element, without proper synchronization mechanisms.
The technical root cause stems from the use of an incorrect list deletion function within the eventfs implementation. The vulnerability occurs when the function eventfs_remove_rec removes an entry from a list using a standard list_del() operation instead of the appropriate list_del_rcu() function, which is required for SRCU-protected lists. This discrepancy creates a scenario where list traversal operations may access memory that has been freed, resulting in a NULL pointer dereference at address dead0000000000000150 as observed in the kernel log. The problem is exacerbated by concurrent operations that simultaneously modify and iterate over the same data structure, creating a classic race condition that violates the expected ordering guarantees of the SRCU mechanism.
The operational impact of this vulnerability is significant as it can cause system instability and potential denial of service conditions. When the kernel panic occurs, the system becomes unresponsive and requires a reboot to recover. The reproduction script provided demonstrates the vulnerability by creating concurrent access patterns that stress the eventfs subsystem through rapid creation and removal of kprobe events while simultaneously iterating over the tracefs directory structure. This scenario mimics real-world conditions where debugging and tracing operations are heavily utilized, making the vulnerability exploitable in environments with active kernel tracing and debugging activities.
The vulnerability aligns with CWE-367, which describes Time-of-Check to Time-of-Use (TOCTOU) race conditions, and also relates to CWE-119, which covers improper access to memory. From an ATT&CK perspective, this vulnerability could be leveraged in a privilege escalation or denial of service attack, as it allows an attacker to trigger a kernel panic through carefully crafted concurrent access patterns. The fix implemented involves switching from list_del() to list_del_rcu() for SRCU-protected lists, which ensures proper synchronization with the SRCU mechanism and prevents access to freed memory. This correction aligns with best practices for concurrent programming in kernel space and addresses the fundamental issue of improper list management in a multi-threaded environment.
Mitigation strategies should focus on applying the kernel patch that corrects the list deletion mechanism. System administrators should prioritize updating to kernel versions that contain the fix, as the vulnerability affects the core kernel functionality and could be exploited by malicious actors to cause system instability. Additionally, monitoring for unusual patterns in tracefs and eventfs operations could help detect potential exploitation attempts. The fix demonstrates the importance of proper synchronization primitives in kernel development and highlights the need for thorough testing of concurrent data structures, particularly those involving SRCU and RCU mechanisms. Organizations should also consider implementing kernel hardening measures and regular security audits to identify similar race condition vulnerabilities in other subsystems.