Bug 2420415 (CVE-2025-40328)

Summary: CVE-2025-40328 kernel: smb: client: fix potential UAF in smb2_close_cached_fid()
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A use-after-free flaw was found in the Linux kernel's SMB client implementation. In smb2_close_cached_fid(), a race condition exists where find_or_create_cached_dir() could acquire a new reference to a cached directory file ID (cfid) after kref_put() observed the reference count drop to zero but before the cfid_list_lock is acquired. This timing gap allows access to freed memory, potentially leading to system instability, data corruption, or privilege escalation.
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Description OSIDB Bzimport 2025-12-09 05:01:52 UTC 
In the Linux kernel, the following vulnerability has been resolved:

smb: client: fix potential UAF in smb2_close_cached_fid()

find_or_create_cached_dir() could grab a new reference after kref_put()
had seen the refcount drop to zero but before cfid_list_lock is acquired
in smb2_close_cached_fid(), leading to use-after-free.

Switch to kref_put_lock() so cfid_release() is called with
cfid_list_lock held, closing that gap.
Comment 1 Alexander B 2025-12-09 13:40:18 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025120909-CVE-2025-40328-a95b@gregkh/T