CVE-2024-50067: Vulnerability in Linux Linux

Severity: highType: vulnerabilityCVE-2024-50067

In the Linux kernel, the following vulnerability has been resolved: uprobe: avoid out-of-bounds memory access of fetching args Uprobe needs to fetch args into a percpu buffer, and then copy to ring buffer to avoid non-atomic context problem. Sometimes user-space strings, arrays can be very large, but the size of percpu buffer is only page size. And store_trace_args() won't check whether these data exceeds a single page or not, caused out-of-bounds memory access. It could be reproduced by following steps: 1. build kernel with CONFIG_KASAN enabled 2. save follow program as test.c ``` \#include <stdio.h> \#include <stdlib.h> \#include <string.h> // If string length large than MAX_STRING_SIZE, the fetch_store_strlen() // will return 0, cause __get_data_size() return shorter size, and // store_trace_args() will not trigger out-of-bounds access. // So make string length less than 4096. \#define STRLEN 4093 void generate_string(char *str, int n) { int i; for (i = 0; i < n; ++i) { char c = i % 26 + 'a'; str[i] = c; } str[n-1] = '\0'; } void print_string(char *str) { printf("%s\n", str); } int main() { char tmp[STRLEN]; generate_string(tmp, STRLEN); print_string(tmp); return 0; } ``` 3. compile program `gcc -o test test.c` 4. get the offset of `print_string()` ``` objdump -t test | grep -w print_string 0000000000401199 g F .text 000000000000001b print_string ``` 5. configure uprobe with offset 0x1199 ``` off=0x1199 cd /sys/kernel/debug/tracing/ echo "p /root/test:${off} arg1=+0(%di):ustring arg2=\$comm arg3=+0(%di):ustring" > uprobe_events echo 1 > events/uprobes/enable echo 1 > tracing_on ``` 6. run `test`, and kasan will report error. ================================================================== BUG: KASAN: use-after-free in strncpy_from_user+0x1d6/0x1f0 Write of size 8 at addr ffff88812311c004 by task test/499CPU: 0 UID: 0 PID: 499 Comm: test Not tainted 6.12.0-rc3+ #18 Hardware name: Red Hat KVM, BIOS 1.16.0-4.al8 04/01/2014 Call Trace: <TASK> dump_stack_lvl+0x55/0x70 print_address_description.constprop.0+0x27/0x310 kasan_report+0x10f/0x120 ? strncpy_from_user+0x1d6/0x1f0 strncpy_from_user+0x1d6/0x1f0 ? rmqueue.constprop.0+0x70d/0x2ad0 process_fetch_insn+0xb26/0x1470 ? __pfx_process_fetch_insn+0x10/0x10 ? _raw_spin_lock+0x85/0xe0 ? __pfx__raw_spin_lock+0x10/0x10 ? __pte_offset_map+0x1f/0x2d0 ? unwind_next_frame+0xc5f/0x1f80 ? arch_stack_walk+0x68/0xf0 ? is_bpf_text_address+0x23/0x30 ? kernel_text_address.part.0+0xbb/0xd0 ? __kernel_text_address+0x66/0xb0 ? unwind_get_return_address+0x5e/0xa0 ? __pfx_stack_trace_consume_entry+0x10/0x10 ? arch_stack_walk+0xa2/0xf0 ? _raw_spin_lock_irqsave+0x8b/0xf0 ? __pfx__raw_spin_lock_irqsave+0x10/0x10 ? depot_alloc_stack+0x4c/0x1f0 ? _raw_spin_unlock_irqrestore+0xe/0x30 ? stack_depot_save_flags+0x35d/0x4f0 ? kasan_save_stack+0x34/0x50 ? kasan_save_stack+0x24/0x50 ? mutex_lock+0x91/0xe0 ? __pfx_mutex_lock+0x10/0x10 prepare_uprobe_buffer.part.0+0x2cd/0x500 uprobe_dispatcher+0x2c3/0x6a0 ? __pfx_uprobe_dispatcher+0x10/0x10 ? __kasan_slab_alloc+0x4d/0x90 handler_chain+0xdd/0x3e0 handle_swbp+0x26e/0x3d0 ? __pfx_handle_swbp+0x10/0x10 ? uprobe_pre_sstep_notifier+0x151/0x1b0 irqentry_exit_to_user_mode+0xe2/0x1b0 asm_exc_int3+0x39/0x40 RIP: 0033:0x401199 Code: 01 c2 0f b6 45 fb 88 02 83 45 fc 01 8b 45 fc 3b 45 e4 7c b7 8b 45 e4 48 98 48 8d 50 ff 48 8b 45 e8 48 01 d0 ce RSP: 002b:00007ffdf00576a8 EFLAGS: 00000206 RAX: 00007ffdf00576b0 RBX: 0000000000000000 RCX: 0000000000000ff2 RDX: 0000000000000ffc RSI: 0000000000000ffd RDI: 00007ffdf00576b0 RBP: 00007ffdf00586b0 R08: 00007feb2f9c0d20 R09: 00007feb2f9c0d20 R10: 0000000000000001 R11: 0000000000000202 R12: 0000000000401040 R13: 00007ffdf0058780 R14: 0000000000000000 R15: 0000000000000000 </TASK> This commit enforces the buffer's maxlen less than a page-size to avoid store_trace_args() out-of-memory access.

AI Analysis

Technical Summary

CVE-2024-50067 is a high-severity vulnerability in the Linux kernel's uprobe subsystem, which is used for dynamic tracing of user-space applications. The flaw arises from an out-of-bounds memory access when fetching arguments into a per-CPU buffer during uprobe event handling. Specifically, uprobe attempts to copy user-space strings or arrays into a per-CPU buffer that is limited to a single page size (typically 4096 bytes). However, the function store_trace_args() does not properly verify whether the data size exceeds this buffer size, leading to potential out-of-bounds memory access. This can cause use-after-free conditions and memory corruption, as demonstrated by the Kernel Address Sanitizer (KASAN) error logs. The vulnerability can be triggered by configuring uprobe events with carefully crafted offsets and arguments, as shown in the provided test case. Exploitation requires local privileges (PR:L) and no user interaction (UI:N), but can result in high impact on confidentiality, integrity, and availability (C:H/I:H/A:H). The vulnerability is present in Linux kernel versions prior to the patch commit referenced, and it has been addressed by enforcing the maximum buffer length to be less than a page size to prevent out-of-bounds access. The CVSS 3.1 score is 7.8, reflecting the high risk posed by this flaw.

Potential Impact

For European organizations, this vulnerability poses a significant risk especially for those running Linux-based servers, workstations, or embedded devices that utilize uprobe for tracing or debugging. Exploitation could allow a local attacker with limited privileges to escalate their rights, execute arbitrary code in kernel context, or cause denial of service via kernel crashes. This could lead to data breaches, service outages, or compromise of critical infrastructure. Since Linux is widely deployed across European enterprises, cloud providers, and public sector systems, the vulnerability could affect a broad range of targets including financial institutions, government agencies, telecommunications, and industrial control systems. The ability to corrupt kernel memory undermines system integrity and confidentiality, potentially enabling attackers to bypass security controls or persist undetected. Although exploitation requires local access, insider threats or attackers who gain initial footholds could leverage this vulnerability to deepen their control over affected systems.

Mitigation Recommendations

European organizations should prioritize updating their Linux kernels to versions that include the fix for CVE-2024-50067. Specifically, ensure that kernel versions are patched to enforce buffer size limits in the uprobe subsystem. For environments where immediate patching is not feasible, consider disabling uprobe tracing features if they are not essential, to reduce the attack surface. Implement strict access controls to limit who can configure or trigger uprobe events, as exploitation requires local privileges. Employ kernel hardening techniques such as Kernel Address Sanitizer (KASAN) during testing phases to detect similar memory issues proactively. Additionally, monitor system logs and kernel tracing outputs for unusual uprobe activity that could indicate exploitation attempts. Regularly audit user privileges and restrict local access to trusted personnel and processes. Finally, incorporate this vulnerability into vulnerability management and incident response plans to ensure timely detection and remediation.