{"id":"CVE-2026-98103","title":"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->lock) to ip_check_mc_rcu() to preve…","summary":"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->lock) to ip_check_mc_rcu() to preve…","severity":"none","vendor":"Linux","product":"Linux","affected":["Linux >= 23d2b94043ca8835bd1e67749020e839f396a1c2 < f5182dfad54277267a8cb0c004a9cd4cf35aeebb","Linux >= 23d2b94043ca8835bd1e67749020e839f396a1c2 < d3011d1f293478c730aa0870490afa145c37600e","Linux >= 23d2b94043ca8835bd1e67749020e839f396a1c2 < e3206419bdb04e2087d8cc6be324df8639b3fac5","Linux >= 23d2b94043ca8835bd1e67749020e839f396a1c2 < 2987ee196c88dbde0463dc87d5fb209c684e34a2","Linux b24065948ae6c48c9e20891f8cfe9850f1d748be","Linux e9924c4204ede999b0515fd31a370a1e27f676bc","Linux 78967749984cf3614de346c90f3e259ff8272735","Linux 4768973dffed4d0126854514335ed4fe87bec1ab","Linux d84708451d9041dff8a81e3718f821f12d2eb6c5","Linux ddd7e8b7b84836c584a284b98ca9bd7a348a0558","Linux 961447ff60291b91e27d5c32fa549c1411ad3b70","Linux d1a3c6d5925a8d00a32c5ef2d674dd9c0ce89c95","Linux >= 4.4.284 < 4.5","Linux >= 4.9.283 < 4.10","Linux >= 4.14.247 < 4.15","Linux >= 4.19.207 < 4.20","Linux >= 5.4.145 < 5.5","Linux >= 5.10.64 < 5.11","Linux >= 5.13.16 < 5.14","Linux >= 5.14.3 < 5.15","Linux 5.15"],"published":"2026-09-25","updated":"2026-09-25","sourceUpdated":"2026-09-25T11:17:40.613","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-98103","references":[{"url":"https://git.kernel.org/stable/c/2987ee196c88dbde0463dc87d5fb209c684e34a2","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/d3011d1f293478c730aa0870490afa145c37600e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e3206419bdb04e2087d8cc6be324df8639b3fac5","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f5182dfad54277267a8cb0c004a9cd4cf35aeebb","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd","cve.org"],"ingestedAt":"2026-09-25T11:06:38.827Z","slug":"CVE-2026-98103","body":"## Overview\n\nIn 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->lock) to ip_check_mc_rcu() to prevent a\nuse-after-free while iterating im->sources 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->lock and\ncalls add_grec() -> igmpv3_newpack() -> ip_route_output_ports(),\nan XFRM policy matching a multicast destination triggers\nxfrm_tmpl_resolve_one() -> xfrm4_get_saddr() -> __mkroute_output() ->\nip_check_mc_rcu(). This attempts to acquire &im->lock while &pmc->lock\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->lock) from ip_check_mc_rcu() and traverse\n   im->sources 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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":3,"depthScoreParts":{"impact":2.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}