high CVSS 7.8

CVE-2024-49854·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: block, bfq: fix uaf for accessing waker_bfqq after splitting After commit 42c306ed7233 ("block, bfq: don't break merge chain in bfq_split_bfqq()"), if the current procress is the last holder of bfqq, the bfqq can be freed after bfq_split_bfqq(). Hence recored the bfqq and then access bfqq->waker_bfqq may trigger UAF. What's more, the waker_bfqq may in the merge chain of bfqq, hence just recored waker_bfqq is still not safe. Fix the problem by adding a helper bfq_waker_bfqq() to check if bfqq->waker_bfqq is in the merge chain, and current procress is the only holder.

Severity
high
Software
Kernel
Fixed in
6.11.2
Published
2024-10-21

Affected versions

From: 6.11

Until: 6.11.2

Fixed in: 6.11.2

How to fix this CVE

Update your Linux kernel to version 6.11.2 or later to resolve a use-after-free vulnerability in the BFQ I/O scheduler that could occur during queue splitting operations. This flaw affects kernel versions 6.11 through 6.11.1 and requires a kernel upgrade followed by a system reboot to take effect.

sudo dnf update kernel kernel-devel && sudo reboot

Defensia detects this vulnerability

How to check if you are affected

  1. Check kernel version: uname -r — vulnerable if output is 6.11.0 or 6.11.1
  2. Verify BFQ scheduler is active: cat /sys/block/sda/queue/scheduler — check if '[bfq]' is listed and enabled
  3. Search kernel logs for UAF indicators: sudo dmesg | grep -i 'use-after-free\|uaf\|bfqq' — look for memory safety violations
  4. Confirm patch applied: grep -i 'bfq_waker_bfqq' /boot/config-$(uname -r) — verify helper function is present in compiled kernel

FAQ

What is CVE-2024-49854?

CVE-2024-49854 is a use-after-free vulnerability in the Linux kernel's BFQ (Budget Fair Queuing) I/O scheduler that occurs when a process is the last holder of a queue during a split operation, potentially allowing memory corruption or kernel panic.

Is CVE-2024-49854 being actively exploited?

No, this vulnerability is not listed on the CISA Known Exploited Vulnerabilities catalog and no public exploits are available. However, it should still be patched promptly due to its high severity rating.

What versions of Kernel are affected by CVE-2024-49854?

Linux kernel versions 6.11.0 and 6.11.1 are affected. The vulnerability has been fixed in version 6.11.2 and later.

How do I check if my server is vulnerable to CVE-2024-49854?

Run 'uname -r' and check if the output is 6.11.0 or 6.11.1. Additionally, verify BFQ is enabled with 'cat /sys/block/*/queue/scheduler' — if 6.11.x with BFQ active, the system is vulnerable.

Does Defensia detect CVE-2024-49854?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If the Linux kernel is installed on a monitored server running 6.11.0 or 6.11.1, CVE-2024-49854 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-2022-48716CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: ASoC: codecs: wcd938x: fix incorrect used of portid Mixer controls have the channel id in mixer->reg, which is not same as port id. port id should be derived from chan_info array. So fix this. Without this, its possible that we could corrupt struct wcd938x_sdw_priv by accessing port_map array out of range with channel id instead of port 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-2024-36031CVSS 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-2024-38541CVSS 9.8In the Linux kernel, the following vulnerability has been resolved: of: module: add buffer overflow check in of_modalias() In of_modalias(), if the buffer happens to be too small even for the 1st snprintf() call, the len parameter will become negative and str parameter (if not NULL initially) will point beyond the buffer's end. Add the buffer overflow check after the 1st snprintf() call and fix such check after the strlen() call (accounting for the terminating NUL char).

References

Track CVEs across your fleet automatically

Defensia scans your Linux servers and tells you exactly which ones are running vulnerable versions — including CVE-2024-49854. Free for 1 server.

Get started free