CVE-2026-98101
Description
In the Linux kernel, the following vulnerability has been resolved: ipv6: mcast: use copy-on-write RCU updates in ip6_mc_source() pmc->sflist is read locklessly under rcu_read_lock() by inet6_mc_check() during packet reception in the UDP and RAW multicast receive paths. ip6_mc_source() mutated psl->sl_addr and psl->sl_count in-place when adding or removing a source filter. Additionally, when expanding the filter buffer, newpsl was published via rcu_assign_pointer() before writing the new source into the array. Because 16-byte struct in6_addr writes are not atomic and array shifting is not synchronized with RCU readers, concurrent readers in inet6_mc_check() could read torn IPv6 addresses or observe duplicated/missed source entries. Fix this by switching ip6_mc_source() to copy-on-write RCU updates: allocate and fully populate newpsl before publishing it via rcu_assign_pointer(), and reclaim the old filter via kfree_rcu(), matching ip6_mc_msfilter(). Also remove the now unused IP6_SFBLOCK macro.
How to fix
- Linux Linuxac51321d3b2391860a935820ebcf4d8b9bb16a8a, dba00514bf668c26cb4900e9f0da84bf96bf065a, 2c2091e2ee93049fc513ad1e6c99d8b6c809f467, 20db91a052332ef5552bd2f651ffb9db911cf67b, c073d1b070f171d206b19c98d71739a97f15b3f1, 5.11 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Linux Linux | 882ba1f73c06831f2a21044ebd8864c485ac04f2 ≤ v < ac51321d3b2391860a935820ebcf4d8b9bb16a8a, 882ba1f73c06831f2a21044ebd8864c485ac04f2 ≤ v < dba00514bf668c26cb4900e9f0da84bf96bf065a, 882ba1f73c06831f2a21044ebd8864c485ac04f2 ≤ v < 2c2091e2ee93049fc513ad1e6c99d8b6c809f467, 882ba1f73c06831f2a21044ebd8864c485ac04f2 ≤ v < 20db91a052332ef5552bd2f651ffb9db911cf67b, 882ba1f73c06831f2a21044ebd8864c485ac04f2 ≤ v < c073d1b070f171d206b19c98d71739a97f15b3f1, 47c75e3923c8d562fea8daf0ccf31546a7bef0ea, 5.10.261 ≤ v < 5.11, 5.13 | ac51321d3b2391860a935820ebcf4d8b9bb16a8a, dba00514bf668c26cb4900e9f0da84bf96bf065a, 2c2091e2ee93049fc513ad1e6c99d8b6c809f467, 20db91a052332ef5552bd2f651ffb9db911cf67b, c073d1b070f171d206b19c98d71739a97f15b3f1, 5.11 |
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