CVE-2025-39673

In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ppp: fix race conditions in ppp_fill_forward_path<br /> <br /> ppp_fill_forward_path() has two race conditions:<br /> <br /> 1. The ppp-&gt;channels list can change between list_empty() and<br /> list_first_entry(), as ppp_lock() is not held. If the only channel<br /> is deleted in ppp_disconnect_channel(), list_first_entry() may<br /> access an empty head or a freed entry, and trigger a panic.<br /> <br /> 2. pch-&gt;chan can be NULL. When ppp_unregister_channel() is called,<br /> pch-&gt;chan is set to NULL before pch is removed from ppp-&gt;channels.<br /> <br /> Fix these by using a lockless RCU approach:<br /> - Use list_first_or_null_rcu() to safely test and access the first list<br /> entry.<br /> - Convert list modifications on ppp-&gt;channels to their RCU variants and<br /> add synchronize_net() after removal.<br /> - Check for a NULL pch-&gt;chan before dereferencing it.