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On Wed, Apr 01, 2026 at 03:58:01PM +0800, Weiming Shi wrote:
> 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, probably for non-canonical address
> 0xdffffc0000000006: 0000 [#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)
> ip_setsockopt (net/ipv4/ip_sockglue.c:1427)
> raw_setsockopt (net/ipv4/raw.c:850)
> do_sock_setsockopt (net/socket.c:2322)
> __sys_setsockopt (net/socket.c:2339)
> __x64_sys_setsockopt (net/socket.c:2350)
> do_syscall_64 (arch/x86/entry/syscall_64.c:94)
> entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:130)
> </TASK>
>
> 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().
>
> Fixes: 05f00505a89a ("ipvs: fix crash if scheduler is changed")
> Reported-by: Xiang Mei <xmei5@xxxxxxx>
> Signed-off-by: Weiming Shi <bestswngs@xxxxxxxxx>
Acked-by: Simon Horman <horms@xxxxxxxxxx>
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