high CVSS 7.8

CVE-2024-26956·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: nilfs2: fix failure to detect DAT corruption in btree and direct mappings Patch series "nilfs2: fix kernel bug at submit_bh_wbc()". This resolves a kernel BUG reported by syzbot. Since there are two flaws involved, I've made each one a separate patch. The first patch alone resolves the syzbot-reported bug, but I think both fixes should be sent to stable, so I've tagged them as such. This patch (of 2): Syzbot has reported a kernel bug in submit_bh_wbc() when writing file data to a nilfs2 file system whose metadata is corrupted. There are two flaws involved in this issue. The first flaw is that when nilfs_get_block() locates a data block using btree or direct mapping, if the disk address translation routine nilfs_dat_translate() fails with internal code -ENOENT due to DAT metadata corruption, it can be passed back to nilfs_get_block(). This causes nilfs_get_block() to misidentify an existing block as non-existent, causing both data block lookup and insertion to fail inconsistently. The second flaw is that nilfs_get_block() returns a successful status in this inconsistent state. This causes the caller __block_write_begin_int() or others to request a read even though the buffer is not mapped, resulting in a BUG_ON check for the BH_Mapped flag in submit_bh_wbc() failing. This fixes the first issue by changing the return value to code -EINVAL when a conversion using DAT fails with code -ENOENT, avoiding the conflicting condition that leads to the kernel bug described above. Here, code -EINVAL indicates that metadata corruption was detected during the block lookup, which will be properly handled as a file system error and converted to -EIO when passing through the nilfs2 bmap layer.

Severity: high
Software: Kernel
Fixed in: 6.8.3
Published: 2024-05-01

Affected versions

From: 6.8

Until: 6.8.3

Fixed in: 6.8.3

How to fix this CVE

Update your Linux kernel to version 6.8.3 or later to fix a critical metadata corruption handling bug in the nilfs2 file system. This vulnerability affects kernel versions 6.8 through 6.8.2 and can trigger kernel panics when writing to corrupted nilfs2 partitions. Systems using nilfs2 should prioritize this update to prevent data integrity issues and system crashes.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

Check installed kernel version: uname -r (should be 6.8.3 or later if patched)
Verify nilfs2 module is loaded: lsmod | grep nilfs2 (indicates if nilfs2 is in use on the system)
List nilfs2 mounted filesystems: mount | grep nilfs2 (identifies systems actively using vulnerable code)
Confirm kernel vulnerability status: grep 'CONFIG_NILFS2' /boot/config-$(uname -r) (checks if nilfs2 support is compiled in)

FAQ

What is CVE-2024-26956?

This vulnerability in nilfs2 causes the kernel to mishandle corrupted disk address translation (DAT) metadata, leading to kernel panics when the filesystem attempts to write data. The bug prevents proper error detection when metadata corruption occurs, causing submit_bh_wbc() to fail with a BUG_ON assertion.

Is CVE-2024-26956 being actively exploited?

No, this vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog and no public exploits are available. However, it can be triggered by corrupted nilfs2 filesystems, whether from hardware failure or malicious corruption.

What versions of Kernel are affected by CVE-2024-26956?

Linux kernel versions 6.8 through 6.8.2 are affected. The fix was introduced in version 6.8.3.

How do I check if my server is vulnerable to CVE-2024-26956?

Run 'uname -r' to check your kernel version. If it shows 6.8.0, 6.8.1, or 6.8.2, your system is vulnerable. Additionally, check if nilfs2 is in use with 'mount | grep nilfs2'—vulnerable only if nilfs2 partitions are present.

Does Defensia detect CVE-2024-26956?

Yes — Defensia's CVE advisory scanner compares installed kernel versions against the NVD database. If a vulnerable kernel version is detected on a monitored server, CVE-2024-26956 will appear in your dashboard with remediation steps.

Related Kernel CVEs

CVE-2024-39462CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: clk: bcm: dvp: Assign ->num before accessing ->hws Commit f316cdff8d67 ("clk: Annotate struct clk_hw_onecell_data with __counted_by") annotated the hws member of 'struct clk_hw_onecell_data' with __counted_by, which informs the bounds sanitizer about the number of elements in hws, so that it can warn when hws is accessed out of bounds. As noted in that change, the __counted_by member must be initialized with the number of elements before the first array access happens, otherwise there will be a warning from each access prior to the initialization because the number of elements is zero. This occurs in clk_dvp_probe() due to ->num being assigned after ->hws has been accessed: UBSAN: array-index-out-of-bounds in drivers/clk/bcm/clk-bcm2711-dvp.c:59:2 index 0 is out of range for type 'struct clk_hw *[] __counted_by(num)' (aka 'struct clk_hw *[]') Move the ->num initialization to before the first access of ->hws, which clears up the warning.

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-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-2024-38612CVSS 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-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.

References

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