In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in...

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

ksmbd: fix use-after-free in same_client_has_lease()

same_client_has_lease() returns an opinfo pointer from ci->m_op_list after dropping ci->m_lock without taking a reference.

smb_grant_oplock() then dereferences that pointer in copy_lease() and when checking breaking_cnt. A concurrent close can remove the old lease from ci->m_op_list and drop the last reference before the caller uses the returned pointer, leading to a use-after-free.

Take a reference when same_client_has_lease() selects an existing lease, drop any previous match while scanning, and release the returned reference in smb_grant_oplock() after copying the lease state.