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CVE-2026-90156: ksmbd: safely discard unregistered deferred locks

• Severity: unknown
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-09-17 · updated 2026-10-30

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: safely discard unregistered deferred locks When vfs_lock_file() defers a lock, smb2_lock() puts its ksmbd_lock on rollback_list before allocating and registering the asynchronous work. If either operation fails, rollback assumes that smb_lock->conn is initialized and dereferences NULL. The deferred file_lock also remains linked into the VFS blocked-lock state while it is freed. Keep the lock off rollback_list until async setup succeeds. On setup failures, explicitly unblock and wake the deferred lock before freeing it and its ksmbd wrapper.

Affected products

• Linux: 5.15 — fixed in 7.3

How to fix

Upgrade to a fixed version: Linux 7.3. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/054bcca4cd9f00719b01f7108b51a2168fb94f15
• https://git.kernel.org/stable/c/52b91bc5253bb83665f3ea70565d0b2487dae643
• https://git.kernel.org/stable/c/77413400f083a959724de6f36348c9677ef9873a
• https://git.kernel.org/stable/c/aaa51ac0d934cb4e2ab96e150fccc934e822009b
• https://git.kernel.org/stable/c/d09af9a35ff7b77a950b507133d9092aadbfeff4
• https://git.kernel.org/stable/c/ecdcfa15b3d799476c685cecd433ebefc93015c8

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