high CVSS 7.8

CVE-2024-36001·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: netfs: Fix the pre-flush when appending to a file in writethrough mode In netfs_perform_write(), when the file is marked NETFS_ICTX_WRITETHROUGH or O_*SYNC or RWF_*SYNC was specified, write-through caching is performed on a buffered file. When setting up for write-through, we flush any conflicting writes in the region and wait for the write to complete, failing if there's a write error to return. The issue arises if we're writing at or above the EOF position because we skip the flush and - more importantly - the wait. This becomes a problem if there's a partial folio at the end of the file that is being written out and we want to make a write to it too. Both the already-running write and the write we start both want to clear the writeback mark, but whoever is second causes a warning looking something like: ------------[ cut here ]------------ R=00000012: folio 11 is not under writeback WARNING: CPU: 34 PID: 654 at fs/netfs/write_collect.c:105 ... CPU: 34 PID: 654 Comm: kworker/u386:27 Tainted: G S ... ... Workqueue: events_unbound netfs_write_collection_worker ... RIP: 0010:netfs_writeback_lookup_folio Fix this by making the flush-and-wait unconditional. It will do nothing if there are no folios in the pagecache and will return quickly if there are no folios in the region specified. Further, move the WBC attachment above the flush call as the flush is going to attach a WBC and detach it again if it is not present - and since we need one anyway we might as well share it.

Severity
high
Software
Kernel
Fixed in
6.8.9
Published
2024-05-20

Affected versions

From: 6.8

Until: 6.8.9

Fixed in: 6.8.9

How to fix this CVE

Update your Linux kernel to version 6.8.9 or later to fix a critical write-through caching bug that can cause kernel warnings and potential data consistency issues when appending to files. This patch ensures proper synchronization of conflicting writes at or beyond the end-of-file position, preventing race conditions in the netfs subsystem.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check current kernel version with `uname -r` and compare against 6.8.0 through 6.8.8
  2. Step 2: Verify if the system uses write-through caching by checking file system mount options with `mount | grep -E '(sync|netfs)'`
  3. Step 3: Search system logs for the warning signature: `grep -r 'is not under writeback' /var/log/` or `dmesg | grep 'netfs_writeback_lookup_folio'`
  4. Step 4: Confirm patch application by verifying kernel version is 6.8.9 or later with `uname -r` after reboot

FAQ

What is CVE-2024-36001?

CVE-2024-36001 is a Linux kernel vulnerability in the netfs write-through caching mechanism that fails to properly synchronize conflicting writes when appending to files at or beyond the end-of-file position, resulting in kernel warnings and potential data coherency issues.

Is CVE-2024-36001 being actively exploited?

No, CVE-2024-36001 is not listed on the CISA KEV catalog and has no known public exploits. It is primarily a reliability issue rather than a security vulnerability.

What versions of Kernel are affected by CVE-2024-36001?

Linux kernel versions 6.8.0 through 6.8.8 are vulnerable. Kernel 6.8.9 and later versions contain the fix.

How do I check if my server is vulnerable to CVE-2024-36001?

Run `uname -r` to display your kernel version. If it reports a version between 6.8.0 and 6.8.8 inclusive, your system is vulnerable.

Does Defensia detect CVE-2024-36001?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2024-36001 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-2024-38612CVSS 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-2024-39462CVSS 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-2024-38541CVSS 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).
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

Track CVEs across your fleet automatically

Defensia scans your Linux servers and tells you exactly which ones are running vulnerable versions — including CVE-2024-36001. Free for 1 server.

Get started free