CVE-2021-47556: linux kernel Null Dereference — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: ethtool: ioctl: fix potential NULL deref in ethtool_set_coalesce() ethtool_set_coalesce() now uses both the .get_coalesce() and .set_coalesce() callbacks. But the check for their availability is buggy, so changing the coalesce settings on a device where the driver provides only _one_ of the callbacks results in a NULL pointer dereference instead of an -EOPNOTSUPP. Fix the condition so that the availability of both callbacks is ensured. This also matches the netlink code. Note that reproducing this requires some effort - it only affects the legacy ioctl path, and needs a specific combination of driver options: - have .get_coalesce() and .coalesce_supported but no .set_coalesce(), or - have .set_coalesce() but no .get_coalesce(). Here eg. ethtool doesn't cause the crash as it first attempts to call ethtool_get_coalesce() and bails out on error.

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linux	linux_kernel	5.15 — 5.15.6

References

Advisories & Patches

https://git.kernel.org/stable/c/0276af2176c78771da7f311621a25d7608045827 https://git.kernel.org/stable/c/abfdd9e2f0f9699015d72317f74154d3e53664e6 https://git.kernel.org/stable/c/0276af2176c78771da7f311621a25d7608045827 https://git.kernel.org/stable/c/abfdd9e2f0f9699015d72317f74154d3e53664e6

Frequently Asked Questions

What is CVE-2021-47556? +

In the Linux kernel, the following vulnerability has been resolved: ethtool: ioctl: fix potential NULL deref in ethtool_set_coalesce() ethtool_set_coalesce() now uses both the .get_coalesce() and .set_coalesce() callbacks. But the check for their availability is buggy, so changing the coalesce settings on a device where the driver provides only _one_ of the callbacks results in a NULL pointer dereference instead of an -EOPNOTSUPP. Fix the condition so that the availability of both callbacks is ensured. This also matches the netlink code. Note that reproducing this requires some effort - it only affects the legacy ioctl path, and needs a specific combination of driver options: - have .get_coalesce() and .coalesce_supported but no .set_coalesce(), or - have .set_coalesce() but no .get_coalesce(). Here eg. ethtool doesn't cause the crash as it first attempts to call ethtool_get_coalesce() and bails out on error. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2021-47556? +

CVE-2021-47556 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2021-47556? +

CVE-2021-47556 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2021-47556? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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CVE-2021-47556