Linux Kernel up to 6.6.3 vfs_getattr_nosec getattr_flags null pointer dereference

Summaryinfo

A vulnerability has been found in Linux Kernel up to 6.6.3 and classified as critical. Affected is the function vfs_getattr_nosec. The manipulation of the argument getattr_flags leads to null pointer dereference. This vulnerability is listed as CVE-2023-52779. There is no available exploit. The affected component should be upgraded.

Detailsinfo

A vulnerability, which was classified as critical, has been found in Linux Kernel up to 6.6.3. This issue affects the function vfs_getattr_nosec. The manipulation of the argument getattr_flags with an unknown input leads to a null pointer dereference vulnerability. Using CWE to declare the problem leads to 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. Impacted is availability. The summary by CVE is:

In the Linux kernel, the following vulnerability has been resolved: fs: Pass AT_GETATTR_NOSEC flag to getattr interface function When vfs_getattr_nosec() calls a filesystem's getattr interface function then the 'nosec' should propagate into this function so that vfs_getattr_nosec() can again be called from the filesystem's gettattr rather than vfs_getattr(). The latter would add unnecessary security checks that the initial vfs_getattr_nosec() call wanted to avoid. Therefore, introduce the getattr flag GETATTR_NOSEC and allow to pass with the new getattr_flags parameter to the getattr interface function. In overlayfs and ecryptfs use this flag to determine which one of the two functions to call. In a recent code change introduced to IMA vfs_getattr_nosec() ended up calling vfs_getattr() in overlayfs, which in turn called security_inode_getattr() on an exiting process that did not have current->fs set anymore, which then caused a kernel NULL pointer dereference. With this change the call to security_inode_getattr() can be avoided, thus avoiding the NULL pointer dereference.

It is possible to read the advisory at git.kernel.org. The identification of this vulnerability is CVE-2023-52779. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 6.6.4 eliminates this vulnerability. Applying the patch 3fb0fa086419/8a924db2d7b5 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

• 6.6.0
• 6.6.1
• 6.6.2
• 6.6.3

License

• open-source

Website

• Vendor: https://www.kernel.org/

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