high CVSS 7.8

CVE-2024-35791·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: KVM: SVM: Flush pages under kvm->lock to fix UAF in svm_register_enc_region() Do the cache flush of converted pages in svm_register_enc_region() before dropping kvm->lock to fix use-after-free issues where region and/or its array of pages could be freed by a different task, e.g. if userspace has __unregister_enc_region_locked() already queued up for the region. Note, the "obvious" alternative of using local variables doesn't fully resolve the bug, as region->pages is also dynamically allocated. I.e. the region structure itself would be fine, but region->pages could be freed. Flushing multiple pages under kvm->lock is unfortunate, but the entire flow is a rare slow path, and the manual flush is only needed on CPUs that lack coherency for encrypted memory.

Severity
high
Software
Kernel
Fixed in
6.7.12
Published
2024-05-17

Affected versions

From: 6.7

Until: 6.7.12

Fixed in: 6.7.12

How to fix this CVE

Update your Linux kernel to version 6.7.12 or later to patch a use-after-free vulnerability in the KVM SVM encrypted region registration code. This issue occurs when memory pages are flushed after releasing the kernel lock, allowing concurrent unregister operations to free the region structure while it is still in use. Apply the kernel update and reboot your system to complete remediation.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check installed kernel version with 'uname -r' and compare against the affected range 6.7.0-6.7.11
  2. Step 2: Verify KVM is enabled and in use by running 'lsmod | grep kvm' and checking for encrypted VM regions with 'cat /proc/cmdline | grep -i sev'
  3. Step 3: Search system logs for UAF-related kernel panics or warnings with 'dmesg | grep -i "use-after-free\|svm_register\|kvm"'
  4. Step 4: After applying the kernel update, run 'uname -r' to confirm version is 6.7.12 or later, then verify with 'sudo dmesg | tail -20' for any related warnings

FAQ

What is CVE-2024-35791?

This vulnerability is a use-after-free flaw in the Linux kernel's KVM (Kernel Virtual Machine) SVM implementation, specifically in the svm_register_enc_region() function. The bug occurs when encrypted memory pages are flushed after the kernel lock is released, allowing a concurrent unregister operation to free the region structure prematurely.

Is CVE-2024-35791 being actively exploited?

No, this vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog and has no public exploits available. However, it remains a high-severity issue requiring timely patching.

What versions of Kernel are affected by CVE-2024-35791?

Linux kernel versions 6.7.0 through 6.7.11 are affected. The vulnerability is resolved in kernel version 6.7.12 and later.

How do I check if my server is vulnerable to CVE-2024-35791?

Run 'uname -r' to display your kernel version. If the output shows a version between 6.7.0 and 6.7.11 inclusive, your system is vulnerable and requires an immediate kernel update.

Does Defensia detect CVE-2024-35791?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel package is installed on a monitored server running versions 6.7.0-6.7.11, CVE-2024-35791 will appear in your dashboard with remediation steps.

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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