CVE-2026-43086
Description
In the Linux kernel, the following vulnerability has been resolved:
ipvs: fix NULL deref in ip_vs_add_service error path
When ip_vs_bind_scheduler() succeeds in ip_vs_add_service(), the local
variable sched is set to NULL. If ip_vs_start_estimator() subsequently
fails, the out_err cleanup calls ip_vs_unbind_scheduler(svc, sched)
with sched == NULL. ip_vs_unbind_scheduler() passes the cur_sched NULL
check (because svc->scheduler was set by the successful bind) but then
dereferences the NULL sched parameter at sched->done_service, causing a
kernel panic at offset 0x30 from NULL.
Oops: general protection fault, [..] [#1] PREEMPT SMP KASAN NOPTI
KASAN: null-ptr-deref in range [0x0000000000000030-0x0000000000000037]
RIP: 0010:ip_vs_unbind_scheduler (net/netfilter/ipvs/ip_vs_sched.c:69)
Call Trace:
<TASK>
ip_vs_add_service.isra.0 (net/netfilter/ipvs/ip_vs_ctl.c:1500)
do_ip_vs_set_ctl (net/netfilter/ipvs/ip_vs_ctl.c:2809)
nf_setsockopt (net/netfilter/nf_sockopt.c:102)
[..]
Fix by simply not clearing the local sched variable after a successful
bind. ip_vs_unbind_scheduler() already detects whether a scheduler is
installed via svc->scheduler, and keeping sched non-NULL ensures the
error path passes the correct pointer to both ip_vs_unbind_scheduler()
and ip_vs_scheduler_put().
While the bug is older, the problem popups in more recent kernels (6.2),
when the new error path is taken after the ip_vs_start_estimator() call.