CVE-2026-72392ipv6: fib6: fix NULL deref in fib6_walk_continue() on multi-batch dump

Official description

In the Linux kernel, the following vulnerability has been resolved: ipv6: fib6: fix NULL deref in fib6_walk_continue() on multi-batch dump inet6_dump_fib() saves its progress in cb->args[1] as a positional index within the current hash chain. Between batches, a concurrent fib6_new_table() can insert a new table at the chain head, shifting all existing entries. The saved index then lands on a different table, causing fib6_dump_table() to set w->root to the wrong table while w->node still points into the previous one. fib6_walk_continue() dereferences w->node->parent (NULL) and panics: BUG: kernel NULL pointer dereference, address: 0000000000000008 RIP: 0010:fib6_walk_continue+0x6e/0x170 Call Trace: <TASK> fib6_dump_table.isra.0+0xc5/0x240 inet6_dump_fib+0xf6/0x420 rtnl_dumpit+0x30/0xa0 netlink_dump+0x15b/0x460 netlink_recvmsg+0x1d6/0x2a0 ____sys_recvmsg+0x17a/0x190 Fix by storing tb->tb6_id in cb->args[1] instead of a positional index. On resume, skip entries until the id matches; a concurrent head-insert can never match the saved id, so the walker always resumes on the correct table.

Affected packages & fixed versions

Affected products (as reported)

References

• https://git.kernel.org/stable/c/ee73a32dd258d4af66831ff006b771e19812b322
• https://git.kernel.org/stable/c/89f9c5fee3c64c5cabc34e65599308fd3c879cf9
• https://git.kernel.org/stable/c/cb90a774a9c6c46961a44949a246fbb61f5f934c
• https://git.kernel.org/stable/c/27210d433a8c5fe6bf7278a04bbaeb49a81d0290
• https://git.kernel.org/stable/c/059efb48dd746518898faaa9b965511009b59639
• https://git.kernel.org/stable/c/d8a01d27873e04bebd357dc87859aa756e0b28b2
• https://git.kernel.org/stable/c/110ccbd28c9444866fcc84ba96a2ad64fa6e95ae
• https://git.kernel.org/stable/c/9facb861dc6b9b9ea9793ef5032a9a826f7a4229