CVE-2023-52583: Resolving Vulnerability in Linux Kernel - Ceph: Fix Deadlock or Deadcode of Misusing dget()

In the world of cybersecurity, vulnerabilities are often exploited by malicious actors to gain unauthorized access to systems, applications, and data. To protect systems and keep them secure, it's crucial to stay informed and up-to-date with the latest CVEs (Common Vulnerabilities and Exposures) identified and resolved in various software. In this post, we will discuss CVE-2023-52583, a vulnerability that has been resolved in the Linux kernel related to the Ceph file system.

CVE-2023-52583 - Vulnerability Details

The vulnerability CVE-2023-52583 pertains to the Linux kernel and is related to the Ceph file system module. The issue lies in the misuse of dget() function, resulting in either a deadlock or deadcode. A deadlock occurs when two or more processes are unable to proceed because they are mutually waiting for one another to release a resource. On the other hand, deadcode refers to a portion of the code that is never executed during the program's runtime and does not contribute to the output of the program.

The root cause of this issue is an incorrect lock order between a dentry and its parent. It is essential to always make sure the parent attains the lock first, which was not ensured in this case. However, this deadcode is never used, and the parent directory is always set from the callers.

Resolution

To resolve this vulnerability, the problematic code snippet has been removed, completely eliminating the deadlock and deadcode issue related to the misuse of dget().

Original references

1. CVE Details
2. Linux Kernel Mailing List

Here's a simplified version of the patch that was applied to fix this vulnerability

--- a/fs/ceph/dir.c
+++ b/fs/ceph/dir.c
@@ -1278,13 +1278,6 @@ static int ceph_init_dentry(struct dentry *dentry, struct dentry *parent)
      spin_lock(&dentry->d_lock);
      if (!dentry->d_fsdata) {
          /* initialize d_fsdata */
-         if (!parent) {
-             /* get parent if isn't provided */
-             parent = dget_parent(dentry);
-             if (IS_ERR(parent)) {
-                 ret = PTR_ERR(parent);
-                 goto err_unlock;
-             }
-         }

          ceph_dentry(dentry) = ceph_alloc_dentry(dentry);
          if (unlikely(!ceph_dentry(dentry))) {
              ret = -ENOMEM;
-             goto err_unlock;
-         }
      }
      spin_unlock(&dentry->d_lock);

-err_unlock:
-     spin_unlock(&dentry->d_lock);
-     return ret;
}

This fix was added to the mainline Linux kernel, ensuring that systems running the updated kernel versions will not be affected by CVE-2023-52583.

Conclusion

CVE-2023-52583, a vulnerability in the Linux kernel related to the Ceph file system module, has been successfully resolved with the removal of a problematic code snippet. Users can now enjoy a more secure and reliable Linux kernel version without deadlocks or deadcodes related to the misuse of the dget() function. For additional security, always ensure your Linux kernel is up-to-date and patched against known vulnerabilities.

Timeline

Published on: 03/06/2024 07:15:06 UTC
Last modified on: 06/27/2024 13:15:53 UTC