Bug 2393202 (CVE-2025-38711)

Summary: CVE-2025-38711 kernel: smb/server: avoid deadlock when linking with ReplaceIfExists
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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OS: Linux   
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Description OSIDB Bzimport 2025-09-04 16:04:48 UTC 
In the Linux kernel, the following vulnerability has been resolved:

smb/server: avoid deadlock when linking with ReplaceIfExists

If smb2_create_link() is called with ReplaceIfExists set and the name
does exist then a deadlock will happen.

ksmbd_vfs_kern_path_locked() will return with success and the parent
directory will be locked.  ksmbd_vfs_remove_file() will then remove the
file.  ksmbd_vfs_link() will then be called while the parent is still
locked.  It will try to lock the same parent and will deadlock.

This patch moves the ksmbd_vfs_kern_path_unlock() call to *before*
ksmbd_vfs_link() and then simplifies the code, removing the file_present
flag variable.
Comment 1 Jon Moroney 2025-09-04 17:18:59 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2025090456-CVE-2025-38711-b653@gregkh/T