CVE-2026-64141

Summary

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix null pointer dereference in compare_guid_key()

session_fd_check() walks the per-inode m_op_list during durable-handle session teardown and sets op->conn = NULL for every opinfo whose conn matched the closing session's connection. The matching opinfo, however, stays linked in its per-ClientGuid lease_table_list entry's lb->lease_list because destroy_lease_table() only runs on full TCP-connection teardown, not on SESSION_LOGOFF.

If the same TCP connection then negotiates a fresh session with the same ClientGuid (ClientGuid is bound to NEGOTIATE, not the session, and is unchanged across LOGOFF + SETUP) and issues a SMB2 CREATE with a lease context on a different inode, find_same_lease_key() walks lb->lease_list, reaches the stale opinfo, and calls compare_guid_key(), which unconditionally dereferences opinfo->conn->ClientGUID. The conn pointer is NULL and the kernel panics.

Reproducer requires only a successful SMB2 SESSION_SETUP and a share configured with 'durable handles = yes'. KASAN report on mainline 70390501d194:

general protection fault, probably for non-canonical address 0xdffffc0000000069: 0000 [#1] SMP KASAN PTI KASAN: null-ptr-deref in range [0x0000000000000348-0x000000000000034f] Workqueue: ksmbd-io handle_ksmbd_work RIP: 0010:bcmp+0x5b/0x230 Call Trace: compare_guid_key+0x4b/0xd0 find_same_lease_key+0x324/0x690 smb2_open+0x6aea/0x8e60 handle_ksmbd_work+0x796/0xee0 …

Faulting address 0x348 is the offset of ClientGUID within struct ksmbd_conn, confirming opinfo->conn was NULL.

Read opinfo->conn once and bail out if it has been cleared by a concurrent session_fd_check(). A half-detached opinfo cannot be the owner of an active lease, so returning 0 is the correct match result.

Affected Software

Weaknesses

References

• https://git.kernel.org/stable/c/e43cb36d4d7827710cfcd48e95e29a507f0d87be
• https://git.kernel.org/stable/c/0836081b394ca074d1b910f2b990ff7b4b4404c7
• https://git.kernel.org/stable/c/cd5c1b75d2f454f625d7dc55bd3ae21d0855f6ad
• https://git.kernel.org/stable/c/af86896ca3239e25a6bd7d352213371265073d38
• https://git.kernel.org/stable/c/4b83cbc4c15f09b000cc06f033f64b0824b6dc87

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