Linux Kernel up to 5.13.3 nfsd nfs3svc_encode_getaclres null pointer dereference

Summaryinfo

A vulnerability identified as critical has been detected in Linux Kernel up to 5.13.3. This issue affects the function nfs3svc_encode_getaclres of the component nfsd. Performing a manipulation results in null pointer dereference. This vulnerability was named CVE-2021-47316. There is no available exploit. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in Linux Kernel up to 5.13.3. It has been classified as critical. This affects the function nfs3svc_encode_getaclres of the component nfsd. The manipulation with an unknown input leads to a null pointer dereference vulnerability. CWE is classifying the issue as CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. This is going to have an impact on availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: nfsd: fix NULL dereference in nfs3svc_encode_getaclres In error cases the dentry may be NULL. Before 20798dfe249a, the encoder also checked dentry and d_really_is_positive(dentry), but that looks like overkill to me--zero status should be enough to guarantee a positive dentry. This isn't the first time we've seen an error-case NULL dereference hidden in the initialization of a local variable in an xdr encoder. But I went back through the other recent rewrites and didn't spot any similar bugs.

The advisory is shared at git.kernel.org. This vulnerability is uniquely identified as CVE-2021-47316 since 05/21/2024. The exploitability is told to be easy. Technical details are known, but no exploit is available.

Upgrading to version 5.13.4 eliminates this vulnerability. Applying the patch 650e6f383a6e/ab1016d39cc0 is able to eliminate this problem. The bugfix is ready for download at git.kernel.org. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

Version

• 5.13.0
• 5.13.1
• 5.13.2
• 5.13.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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