Bug 2393175 (CVE-2025-38692)

Summary: CVE-2025-38692 kernel: exfat: add cluster chain loop check for dir
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the exfat module in the Linux kernel. An infinite loop issue can be triggered by specific file system corruption conditions, resulting in a denial of service.
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Description OSIDB Bzimport 2025-09-04 16:02:51 UTC
In the Linux kernel, the following vulnerability has been resolved:

exfat: add cluster chain loop check for dir

An infinite loop may occur if the following conditions occur due to
file system corruption.

(1) Condition for exfat_count_dir_entries() to loop infinitely.
    - The cluster chain includes a loop.
    - There is no UNUSED entry in the cluster chain.

(2) Condition for exfat_create_upcase_table() to loop infinitely.
    - The cluster chain of the root directory includes a loop.
    - There are no UNUSED entry and up-case table entry in the cluster
      chain of the root directory.

(3) Condition for exfat_load_bitmap() to loop infinitely.
    - The cluster chain of the root directory includes a loop.
    - There are no UNUSED entry and bitmap entry in the cluster chain
      of the root directory.

(4) Condition for exfat_find_dir_entry() to loop infinitely.
    - The cluster chain includes a loop.
    - The unused directory entries were exhausted by some operation.

(5) Condition for exfat_check_dir_empty() to loop infinitely.
    - The cluster chain includes a loop.
    - The unused directory entries were exhausted by some operation.
    - All files and sub-directories under the directory are deleted.

This commit adds checks to break the above infinite loop.