high CVSS 7.1

CVE-2021-47153·Kernel vulnerability

In the Linux kernel, the following vulnerability has been resolved: i2c: i801: Don't generate an interrupt on bus reset Now that the i2c-i801 driver supports interrupts, setting the KILL bit in a attempt to recover from a timed out transaction triggers an interrupt. Unfortunately, the interrupt handler (i801_isr) is not prepared for this situation and will try to process the interrupt as if it was signaling the end of a successful transaction. In the case of a block transaction, this can result in an out-of-range memory access. This condition was reproduced several times by syzbot: https://syzkaller.appspot.com/bug?extid=ed71512d469895b5b34e https://syzkaller.appspot.com/bug?extid=8c8dedc0ba9e03f6c79e https://syzkaller.appspot.com/bug?extid=c8ff0b6d6c73d81b610e https://syzkaller.appspot.com/bug?extid=33f6c360821c399d69eb https://syzkaller.appspot.com/bug?extid=be15dc0b1933f04b043a https://syzkaller.appspot.com/bug?extid=b4d3fd1dfd53e90afd79 So disable interrupts while trying to reset the bus. Interrupts will be enabled again for the following transaction.

Severity: high
Software: Kernel
Fixed in: 5.12.9
Published: 2024-03-25

Affected versions

From: 5.11

Until: 5.12.9

Fixed in: 5.12.9

How to fix this CVE

Update your Linux kernel to version 5.12.9 or later to resolve this i2c-i801 driver interrupt handling vulnerability. The vulnerability occurs when the driver attempts a bus reset during transaction timeouts, causing the interrupt handler to misprocess the signal and potentially trigger out-of-range memory access. Apply the update immediately to systems running kernel versions 5.11 through 5.12.8.

sudo dnf update kernel

Defensia detects this vulnerability

How to check if you are affected

Step 1: Check your current kernel version by running `uname -r` and verify it falls within the vulnerable range (5.11.x through 5.12.8)
Step 2: Determine if i2c-i801 driver is loaded on your system by executing `lsmod | grep i2c_i801`
Step 3: Search system logs for i2c bus timeout and reset events using `grep -i 'i2c.*timeout\|KILL.*bit' /var/log/kern.log /var/log/messages`
Step 4: After kernel update, reboot the system and verify the new version with `uname -r` to confirm the fix is applied

FAQ

What is CVE-2021-47153?

CVE-2021-47153 is a kernel vulnerability in the i2c-i801 driver where improper interrupt handling during bus reset operations can cause out-of-range memory access, particularly during block transactions. The vulnerability was introduced when interrupt support was added to the driver without accounting for reset scenarios.

Is CVE-2021-47153 being actively exploited?

No, there is no evidence of active exploitation in the wild, and no public exploits are available. However, the vulnerability was reliably reproduced by automated kernel fuzz testing, indicating it poses a real denial-of-service risk.

What versions of Kernel are affected by CVE-2021-47153?

Linux kernel versions 5.11.x through 5.12.8 are affected. The vulnerability is fixed in kernel 5.12.9 and later.

How do I check if my server is vulnerable to CVE-2021-47153?

Run `uname -r` to check your kernel version. If it shows a version between 5.11 and 5.12.8, your system is vulnerable. Additionally, verify the i2c-i801 driver is present with `lsmod | grep i2c_i801`.

Does Defensia detect CVE-2021-47153?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Kernel is installed on a monitored server, CVE-2021-47153 will appear in your dashboard with remediation steps.

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References

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