CVE-2026-89486ipmi: Fix use-after-free of cmd_rcvr in _ipmi_destroy_user()

Official description

In the Linux kernel, the following vulnerability has been resolved: ipmi: Fix use-after-free of cmd_rcvr in _ipmi_destroy_user() Commit 9e91f8a6c868 ("ipmi:msghandler: Remove srcu for the ipmi_interfaces list") dropped the synchronize_rcu() between unlinking the command receivers from intf->cmd_rcvrs and freeing them, updating only the comment that explains why the barrier is needed. The cmd_rcvrs list is still traversed under plain RCU: find_cmd_rcvr() walks it inside rcu_read_lock(), and handle_ipmb_get_msg_cmd() borrows rcvr->user from that lookup within the same read-side section. Without the grace period, _ipmi_destroy_user() can kfree() a cmd_rcvr while a reader still holds a pointer to it, causing a use-after-free. The rework only made srcu unnecessary for the interfaces list; the cmd_rcvrs list still relies on plain RCU. Restore the synchronize_rcu() before freeing the receivers.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/3088e41292fecf132f85f79af5ee4d620b9ff1b4
• https://git.kernel.org/stable/c/5dc0b2a9af95a97861c1bffaf1687a3173e395c5
• https://git.kernel.org/stable/c/05ec76cfbce653e07cec19b9b8b20e33449d5d87