{"id":"AZL-104577","summary":"CVE-2026-98103 affecting package kernel 6.6.157.1-1","details":"In the Linux kernel, the following vulnerability has been resolved:\n\nigmp: convert struct ip_sf_list to RCU\n\nCommit 23d2b94043ca (\"igmp: Add ip_mc_list lock in ip_check_mc_rcu\")\nadded spin_lock_bh(&im-\u003elock) to ip_check_mc_rcu() to prevent a\nuse-after-free while iterating im-\u003esources during concurrent deletions.\n\nHowever, ip_check_mc_rcu() is called from RCU read-side critical\nsections in packet receive and route lookup fast paths (e.g.\n__mkroute_output(), ip_route_input_rcu(), and __udp4_lib_rcv()).\n\nWhen igmpv3_send_cr() or igmpv3_send_report() holds &pmc-\u003elock and\ncalls add_grec() -\u003e igmpv3_newpack() -\u003e ip_route_output_ports(),\nan XFRM policy matching a multicast destination triggers\nxfrm_tmpl_resolve_one() -\u003e xfrm4_get_saddr() -\u003e __mkroute_output() -\u003e\nip_check_mc_rcu(). This attempts to acquire &im-\u003elock while &pmc-\u003elock\nis already held on the same CPU, triggering a lockdep recursive locking\nwarning / deadlock.\n\nFix this by converting IPv4 struct ip_sf_list to RCU, mirroring the\nIPv6 implementation in net/ipv6/mcast.c:\n\n1. Add struct rcu_head to struct ip_sf_list and annotate sf_next,\n   sources, and tomb as __rcu pointers.\n2. Use rcu_assign_pointer() and kfree_rcu() for list updates and\n   deletions.\n3. Remove spin_lock_bh(&im-\u003elock) from ip_check_mc_rcu() and traverse\n   im-\u003esources locklessly with for_each_psf_rcu(), reading and writing\n   counter fields with READ_ONCE() and WRITE_ONCE().\n\nNote: RCU conversion of /proc/net/mcfilter will be done in a\nseparate patch.","modified":"2026-09-27T05:34:32Z","published":"2026-09-25T11:17:40Z","upstream":["CVE-2026-98103"],"references":[{"type":"WEB","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98103"}],"affected":[{"package":{"name":"kernel","ecosystem":"Azure Linux:3","purl":"pkg:rpm/azure-linux/kernel"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"6.6.157.1-1"}]}],"database_specific":{"source":"https://github.com/microsoft/AzureLinuxVulnerabilityData/blob/main/osv/AZL-104577.json"}}],"schema_version":"1.9.0"}