high CVSS 7.1

CVE-2021-47004·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: f2fs: fix to avoid touching checkpointed data in get_victim() In CP disabling mode, there are two issues when using LFS or SSR | AT_SSR mode to select victim: 1. LFS is set to find source section during GC, the victim should have no checkpointed data, since after GC, section could not be set free for reuse. Previously, we only check valid chpt blocks in current segment rather than section, fix it. 2. SSR | AT_SSR are set to find target segment for writes which can be fully filled by checkpointed and newly written blocks, we should never select such segment, otherwise it can cause panic or data corruption during allocation, potential case is described as below: a) target segment has 'n' (n < 512) ckpt valid blocks b) GC migrates 'n' valid blocks to other segment (segment is still in dirty list) c) GC migrates '512 - n' blocks to target segment (segment has 'n' cp_vblocks and '512 - n' vblocks) d) If GC selects target segment via {AT,}SSR allocator, however there is no free space in targe segment.

Severity
high
Software
Kernel
Fixed in
5.12.5
Published
2024-02-28

Affected versions

From: 5.12

Until: 5.12.5

Fixed in: 5.12.5

How to fix this CVE

Update your Linux kernel to version 5.12.5 or later to resolve a critical garbage collection issue that could cause data corruption when CP (checkpoint) disabling mode is enabled with LFS or SSR allocation strategies. The vulnerability stems from improper victim segment selection during garbage collection, which can lead to allocation failures or filesystem corruption. Apply this kernel update immediately through your distribution's package manager.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check your current kernel version: uname -r
  2. Verify if F2FS filesystem is in use: mount | grep f2fs or cat /proc/filesystems | grep f2fs
  3. Check if CP disabling mode is enabled: cat /sys/fs/f2fs/*/cp_disable (returns 1 if enabled)
  4. Inspect kernel logs for GC-related errors: dmesg | grep -i 'garbage collection\|allocation failed\|panic'
  5. After patching, reboot and confirm new kernel version: uname -r (should be 5.12.5 or higher)

FAQ

What is CVE-2021-47004?

CVE-2021-47004 is a vulnerability in the Linux F2FS filesystem's garbage collection routine that fails to properly validate victim segment selection when checkpoint disabling mode is active. This can cause the GC allocator to select segments containing checkpoint data, leading to allocation failures, kernel panics, or data corruption.

Is CVE-2021-47004 being actively exploited?

No, this CVE is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available. However, it poses a serious risk to systems using F2FS with CP disabling mode enabled in production.

What versions of Kernel are affected by CVE-2021-47004?

Linux kernel versions 5.12 through 5.12.4 are affected. The vulnerability was fixed in kernel 5.12.5 and all subsequent releases.

How do I check if my server is vulnerable to CVE-2021-47004?

Run 'uname -r' to check your kernel version; if it shows 5.12.0 to 5.12.4, you are vulnerable. Additionally, run 'mount | grep f2fs' to confirm F2FS is in use, and 'cat /sys/fs/f2fs/*/cp_disable' to check if checkpoint disabling is enabled.

Does Defensia detect CVE-2021-47004?

Yes — Defensia's CVE advisory scanner compares installed kernel package versions against the NVD database. If a Linux kernel in the vulnerable range is detected on a monitored server, CVE-2021-47004 will appear in your dashboard with distribution-specific remediation steps and priority alerts.

Related Kernel CVEs

CVE-2024-42256CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: cifs: Fix server re-repick on subrequest retry When a subrequest is marked for needing retry, netfs will call cifs_prepare_write() which will make cifs repick the server for the op before renegotiating credits; it then calls cifs_issue_write() which invokes smb2_async_writev() - which re-repicks the server. If a different server is then selected, this causes the increment of server->in_flight to happen against one record and the decrement to happen against another, leading to misaccounting. Fix this by just removing the repick code in smb2_async_writev(). As this is only called from netfslib-driven code, cifs_prepare_write() should always have been called first, and so server should never be NULL and the preparatory step is repeated in the event that we do a retry. The problem manifests as a warning looking something like: WARNING: CPU: 4 PID: 72896 at fs/smb/client/smb2ops.c:97 smb2_add_credits+0x3f0/0x9e0 [cifs] ... RIP: 0010:smb2_add_credits+0x3f0/0x9e0 [cifs] ... smb2_writev_callback+0x334/0x560 [cifs] cifs_demultiplex_thread+0x77a/0x11b0 [cifs] kthread+0x187/0x1d0 ret_from_fork+0x34/0x60 ret_from_fork_asm+0x1a/0x30 Which may be triggered by a number of different xfstests running against an Azure server in multichannel mode. generic/249 seems the most repeatable, but generic/215, generic/249 and generic/308 may also show it.
CVE-2024-36031CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: keys: Fix overwrite of key expiration on instantiation The expiry time of a key is unconditionally overwritten during instantiation, defaulting to turn it permanent. This causes a problem for DNS resolution as the expiration set by user-space is overwritten to TIME64_MAX, disabling further DNS updates. Fix this by restoring the condition that key_set_expiry is only called when the pre-parser sets a specific expiry.
CVE-2024-38612CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ipv6: sr: fix invalid unregister error path The error path of seg6_init() is wrong in case CONFIG_IPV6_SEG6_LWTUNNEL is not defined. In that case if seg6_hmac_init() fails, the genl_unregister_family() isn't called. This issue exist since commit 46738b1317e1 ("ipv6: sr: add option to control lwtunnel support"), and commit 5559cea2d5aa ("ipv6: sr: fix possible use-after-free and null-ptr-deref") replaced unregister_pernet_subsys() with genl_unregister_family() in this error path.
CVE-2024-38623CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: fs/ntfs3: Use variable length array instead of fixed size Should fix smatch warning: ntfs_set_label() error: __builtin_memcpy() 'uni->name' too small (20 vs 256)
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.

References

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