critical CVSS 9.8

CVE-2021-47274·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: tracing: Correct the length check which causes memory corruption We've suffered from severe kernel crashes due to memory corruption on our production environment, like, Call Trace: [1640542.554277] general protection fault: 0000 [#1] SMP PTI [1640542.554856] CPU: 17 PID: 26996 Comm: python Kdump: loaded Tainted:G [1640542.556629] RIP: 0010:kmem_cache_alloc+0x90/0x190 [1640542.559074] RSP: 0018:ffffb16faa597df8 EFLAGS: 00010286 [1640542.559587] RAX: 0000000000000000 RBX: 0000000000400200 RCX: 0000000006e931bf [1640542.560323] RDX: 0000000006e931be RSI: 0000000000400200 RDI: ffff9a45ff004300 [1640542.560996] RBP: 0000000000400200 R08: 0000000000023420 R09: 0000000000000000 [1640542.561670] R10: 0000000000000000 R11: 0000000000000000 R12: ffffffff9a20608d [1640542.562366] R13: ffff9a45ff004300 R14: ffff9a45ff004300 R15: 696c662f65636976 [1640542.563128] FS: 00007f45d7c6f740(0000) GS:ffff9a45ff840000(0000) knlGS:0000000000000000 [1640542.563937] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [1640542.564557] CR2: 00007f45d71311a0 CR3: 000000189d63e004 CR4: 00000000003606e0 [1640542.565279] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [1640542.566069] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [1640542.566742] Call Trace: [1640542.567009] anon_vma_clone+0x5d/0x170 [1640542.567417] __split_vma+0x91/0x1a0 [1640542.567777] do_munmap+0x2c6/0x320 [1640542.568128] vm_munmap+0x54/0x70 [1640542.569990] __x64_sys_munmap+0x22/0x30 [1640542.572005] do_syscall_64+0x5b/0x1b0 [1640542.573724] entry_SYSCALL_64_after_hwframe+0x44/0xa9 [1640542.575642] RIP: 0033:0x7f45d6e61e27 James Wang has reproduced it stably on the latest 4.19 LTS. After some debugging, we finally proved that it's due to ftrace buffer out-of-bound access using a debug tool as follows: [ 86.775200] BUG: Out-of-bounds write at addr 0xffff88aefe8b7000 [ 86.780806] no_context+0xdf/0x3c0 [ 86.784327] __do_page_fault+0x252/0x470 [ 86.788367] do_page_fault+0x32/0x140 [ 86.792145] page_fault+0x1e/0x30 [ 86.795576] strncpy_from_unsafe+0x66/0xb0 [ 86.799789] fetch_memory_string+0x25/0x40 [ 86.804002] fetch_deref_string+0x51/0x60 [ 86.808134] kprobe_trace_func+0x32d/0x3a0 [ 86.812347] kprobe_dispatcher+0x45/0x50 [ 86.816385] kprobe_ftrace_handler+0x90/0xf0 [ 86.820779] ftrace_ops_assist_func+0xa1/0x140 [ 86.825340] 0xffffffffc00750bf [ 86.828603] do_sys_open+0x5/0x1f0 [ 86.832124] do_syscall_64+0x5b/0x1b0 [ 86.835900] entry_SYSCALL_64_after_hwframe+0x44/0xa9 commit b220c049d519 ("tracing: Check length before giving out the filter buffer") adds length check to protect trace data overflow introduced in 0fc1b09ff1ff, seems that this fix can't prevent overflow entirely, the length check should also take the sizeof entry->array[0] into account, since this array[0] is filled the length of trace data and occupy addtional space and risk overflow.

Severity
critical
Software
Kernel
Fixed in
5.12.11
Published
2024-05-21

Affected versions

From: 5.11

Until: 5.12.11

Fixed in: 5.12.11

How to fix this CVE

Update your Linux kernel to version 5.12.11 or later to patch the ftrace buffer length validation flaw. This vulnerability allows out-of-bounds memory writes in the tracing subsystem when using kprobe and uprobes with string operations. Prioritize this update immediately given the critical CVSS score of 9.8, as unpatched systems are susceptible to kernel crashes and memory corruption.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check your current kernel version: uname -r | grep -E '^5\.(11|12\.[0-9]|12\.1[0])' && echo 'VULNERABLE' || echo 'NOT VULNERABLE'
  2. Verify if ftrace and kprobe tracing are active: cat /proc/sys/kernel/ftrace_enabled && cat /sys/kernel/debug/tracing/events/kprobes/enable (if values are 1, tracing is enabled)
  3. Search kernel logs for memory corruption or general protection faults: sudo dmesg | grep -i 'general protection fault\|out-of-bounds\|memory corruption' | tail -20
  4. After patching, confirm the updated kernel version: uname -r and verify it is 5.12.11 or later

FAQ

What is CVE-2021-47274?

CVE-2021-47274 is a critical kernel vulnerability in the ftrace subsystem where the length validation for trace buffer entries is insufficient, failing to account for the array header size. This allows attackers to write beyond allocated buffer boundaries, causing kernel memory corruption and crashes.

Is CVE-2021-47274 being actively exploited?

No, according to CISA's Known Exploited Vulnerabilities (KEV) catalog, CVE-2021-47274 is not currently being actively exploited in the wild. However, it is a local privilege escalation vector and should still be patched immediately due to its critical severity.

What versions of Kernel are affected by CVE-2021-47274?

Linux kernel versions 5.11 through 5.12.10 are vulnerable. The fix was released in version 5.12.11 and has been backported to stable branches.

How do I check if my server is vulnerable to CVE-2021-47274?

Run: uname -r && if [[ $(uname -r | sed 's/.*5\.\([0-9]*\)\.\([0-9]*\).*/\1 \2/') =~ ^(11|12\ [0-9]|12\ 10)$ ]]; then echo 'VULNERABLE'; else echo 'PATCHED'; fi

Does Defensia detect CVE-2021-47274?

Yes — Defensia's CVE advisory scanner compares installed kernel versions against the NVD database. If the Linux kernel is installed on a monitored server, CVE-2021-47274 will appear in your dashboard with remediation steps and patch recommendations.

Related Kernel CVEs

CVE-2021-47378CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: nvme-rdma: destroy cm id before destroy qp to avoid use after free We should always destroy cm_id before destroy qp to avoid to get cma event after qp was destroyed, which may lead to use after free. In RDMA connection establishment error flow, don't destroy qp in cm event handler.Just report cm_error to upper level, qp will be destroy in nvme_rdma_alloc_queue() after destroy cm id.
CVE-2021-47548CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ethernet: hisilicon: hns: hns_dsaf_misc: fix a possible array overflow in hns_dsaf_ge_srst_by_port() The if statement: if (port >= DSAF_GE_NUM) return; limits the value of port less than DSAF_GE_NUM (i.e., 8). However, if the value of port is 6 or 7, an array overflow could occur: port_rst_off = dsaf_dev->mac_cb[port]->port_rst_off; because the length of dsaf_dev->mac_cb is DSAF_MAX_PORT_NUM (i.e., 6). To fix this possible array overflow, we first check port and if it is greater than or equal to DSAF_MAX_PORT_NUM, the function returns.
CVE-2024-9194CVSS 9.8Improper Neutralization of Special Elements used in an SQL Command ('SQL Injection') vulnerability in Linux and Microsoft Windows Octopus Server on Windows, Linux allows SQL Injection.This issue affects Octopus Server: from 2024.1.0 before 2024.1.13038, from 2024.2.0 before 2024.2.9482, from 2024.3.0 before 2024.3.12766.
CVE-2024-0132CVSS 9NVIDIA Container Toolkit 1.16.1 or earlier contains a Time-of-check Time-of-Use (TOCTOU) vulnerability when used with default configuration where a specifically crafted container image may gain access to the host file system. This does not impact use cases where CDI is used. A successful exploit of this vulnerability may lead to code execution, denial of service, escalation of privileges, information disclosure, and data tampering.
CVE-2024-36971CVSS 7.8In the Linux kernel, the following vulnerability has been resolved: net: fix __dst_negative_advice() race __dst_negative_advice() does not enforce proper RCU rules when sk->dst_cache must be cleared, leading to possible UAF. RCU rules are that we must first clear sk->sk_dst_cache, then call dst_release(old_dst). Note that sk_dst_reset(sk) is implementing this protocol correctly, while __dst_negative_advice() uses the wrong order. Given that ip6_negative_advice() has special logic against RTF_CACHE, this means each of the three ->negative_advice() existing methods must perform the sk_dst_reset() themselves. Note the check against NULL dst is centralized in __dst_negative_advice(), there is no need to duplicate it in various callbacks. Many thanks to Clement Lecigne for tracking this issue. This old bug became visible after the blamed commit, using UDP sockets.

References

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