Overview
About vulnerability
In the Linux kernel, the following vulnerability has been resolved:
ipmi: Fix user refcount underflow in event delivery
ipmi_alloc_recv_msg(user) takes the temporary user reference owned by the receive message, and ipmi_free_recv_msg() drops it again. If event delivery fails after allocating receive messages for earlier users, handle_read_event_rsp() rolls those messages back with ipmi_free_recv_msg().
That rollback path still drops user->refcount explicitly after freeing each message. The extra put can free a user that remains linked on intf->users, so later event delivery may dereference a freed user or trip refcount_t’s addition-on-zero warning when ipmi_alloc_recv_msg() tries to acquire another reference.
Remove the stale explicit put and the now-dead user assignment. Keep the list_del() and ipmi_free_recv_msg() calls; they are the required rollback operations.
Details
- Affected product:
- Debian 10 ELS
- Affected packages:
- linux @ 4.19.0