From: Xiang Mei (Microsoft) Date: Mon, 13 Jul 2026 22:15:51 +0000 (+0000) Subject: nexthop: initialize extack in nh_res_bucket_migrate() X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=6347c5314cee49f364aaf2e40ff15415a57a116e;p=thirdparty%2Fkernel%2Flinux.git nexthop: initialize extack in nh_res_bucket_migrate() nh_res_bucket_migrate() passes an uninitialized netlink_ext_ack to call_nexthop_res_bucket_notifiers(). When nh_notifier_res_bucket_info_init() fails (e.g. the kzalloc returns -ENOMEM), the error is propagated back before any notifier sets extack._msg, and the error path formats the stale pointer with pr_err_ratelimited("%s\n", extack._msg). With CONFIG_INIT_STACK_NONE this dereferences uninitialized stack memory: Oops: general protection fault, probably for non-canonical address ... KASAN: maybe wild-memory-access in range [...] RIP: 0010:string (lib/vsprintf.c:730) vsnprintf (lib/vsprintf.c:2945) _printk (kernel/printk/printk.c:2504) nh_res_bucket_migrate (net/ipv4/nexthop.c:1816) nh_res_table_upkeep (net/ipv4/nexthop.c:1866) rtm_new_nexthop (net/ipv4/nexthop.c:3323) rtnetlink_rcv_msg (net/core/rtnetlink.c:7076) netlink_sendmsg (net/netlink/af_netlink.c:1900) Kernel panic - not syncing: Fatal exception Zero-initialize extack so _msg is NULL on error paths that never set it. Fixes: 7c37c7e00411 ("nexthop: Implement notifiers for resilient nexthop groups") Reported-by: AutonomousCodeSecurity@microsoft.com Signed-off-by: Xiang Mei (Microsoft) Reviewed-by: Ido Schimmel Link: https://patch.msgid.link/20260713221551.3344650-1-xmei5@asu.edu Signed-off-by: Jakub Kicinski --- diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c index 6205bd57aa85..44fe75004cac 100644 --- a/net/ipv4/nexthop.c +++ b/net/ipv4/nexthop.c @@ -1788,8 +1788,8 @@ static bool nh_res_bucket_migrate(struct nh_res_table *res_table, bool notify_nl, bool force) { struct nh_res_bucket *bucket = &res_table->nh_buckets[bucket_index]; + struct netlink_ext_ack extack = {}; struct nh_grp_entry *new_nhge; - struct netlink_ext_ack extack; int err; new_nhge = list_first_entry_or_null(&res_table->uw_nh_entries,