high CVSS 8.8

CVE-2021-47323·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: watchdog: sc520_wdt: Fix possible use-after-free in wdt_turnoff() This module's remove path calls del_timer(). However, that function does not wait until the timer handler finishes. This means that the timer handler may still be running after the driver's remove function has finished, which would result in a use-after-free. Fix by calling del_timer_sync(), which makes sure the timer handler has finished, and unable to re-schedule itself.

Severity
high
Software
Kernel
Fixed in
5.13.4
Published
2024-05-21

Affected versions

From: 5.13

Until: 5.13.4

Fixed in: 5.13.4

How to fix this CVE

Update your Linux kernel to version 5.13.4 or later to resolve a use-after-free vulnerability in the SC520 watchdog driver. The vulnerability occurs when the watchdog timer handler continues executing after the driver is unloaded, potentially causing memory corruption or system instability. Apply the patch immediately to systems running kernel versions 5.13.0 through 5.13.3.

sudo dnf update kernel kernel-devel

Defensia detects this vulnerability

How to check if you are affected

  1. Check your kernel version: uname -r — if it shows 5.13.0 through 5.13.3, your system is vulnerable
  2. Verify if the SC520 watchdog driver is loaded: lsmod | grep sc520_wdt — if output appears, the vulnerable module is active
  3. Check dmesg for watchdog-related errors: dmesg | grep -i watchdog — look for timer or module-related warnings
  4. After patching, reboot and confirm the new kernel version: uname -r should show 5.13.4 or later

FAQ

What is CVE-2021-47323?

This CVE is a use-after-free vulnerability in the Linux kernel's SC520 watchdog driver where the timer handler may continue running after the driver is removed from memory, potentially leading to system crashes or code execution.

Is CVE-2021-47323 being actively exploited?

No, this vulnerability is not listed in CISA's KEV catalog and no public exploits are currently available, though it should still be patched due to its high severity and potential impact on system stability.

What versions of Kernel are affected by CVE-2021-47323?

Linux kernel versions 5.13.0 through 5.13.3 are vulnerable; kernel 5.13.4 and later contain the fix.

How do I check if my server is vulnerable to CVE-2021-47323?

Run uname -r and check if the output is 5.13.0, 5.13.1, 5.13.2, or 5.13.3; also verify if the SC520 watchdog module is loaded with lsmod | grep sc520_wdt.

Does Defensia detect CVE-2021-47323?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47323 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

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