6.16-stable review patch. If anyone has any objections, please let me know.
------------------
From: Eric Dumazet edumazet@google.com
[ Upstream commit 9f74c0ea9b26d1505d55b61e36b1623dd347e1d1 ]
syzbot reported a WARNING in est_timer() [1]
Problem here is that with CONFIG_PREEMPT_RT=y, timer callbacks can be preempted.
Adopt preempt_disable_nested()/preempt_enable_nested() to fix this.
[1] WARNING: CPU: 0 PID: 16 at ./include/linux/seqlock.h:221 __seqprop_assert include/linux/seqlock.h:221 [inline] WARNING: CPU: 0 PID: 16 at ./include/linux/seqlock.h:221 est_timer+0x6dc/0x9f0 net/core/gen_estimator.c:93 Modules linked in: CPU: 0 UID: 0 PID: 16 Comm: ktimers/0 Not tainted syzkaller #0 PREEMPT_{RT,(full)} Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025 RIP: 0010:__seqprop_assert include/linux/seqlock.h:221 [inline] RIP: 0010:est_timer+0x6dc/0x9f0 net/core/gen_estimator.c:93 Call Trace: <TASK> call_timer_fn+0x17e/0x5f0 kernel/time/timer.c:1747 expire_timers kernel/time/timer.c:1798 [inline] __run_timers kernel/time/timer.c:2372 [inline] __run_timer_base+0x648/0x970 kernel/time/timer.c:2384 run_timer_base kernel/time/timer.c:2393 [inline] run_timer_softirq+0xb7/0x180 kernel/time/timer.c:2403 handle_softirqs+0x22c/0x710 kernel/softirq.c:579 __do_softirq kernel/softirq.c:613 [inline] run_ktimerd+0xcf/0x190 kernel/softirq.c:1043 smpboot_thread_fn+0x53f/0xa60 kernel/smpboot.c:160 kthread+0x70e/0x8a0 kernel/kthread.c:463 ret_from_fork+0x3fc/0x770 arch/x86/kernel/process.c:148 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245 </TASK>
Fixes: d2d6422f8bd1 ("x86: Allow to enable PREEMPT_RT.") Reported-by: syzbot+72db9ee39db57c3fecc5@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/68adf6fa.a70a0220.3cafd4.0000.GAE@google.com/... Signed-off-by: Eric Dumazet edumazet@google.com Reviewed-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Link: https://patch.msgid.link/20250827162352.3960779-1-edumazet@google.com Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- net/core/gen_estimator.c | 2 ++ 1 file changed, 2 insertions(+)
diff --git a/net/core/gen_estimator.c b/net/core/gen_estimator.c index 7d426a8e29f30..f112156db587b 100644 --- a/net/core/gen_estimator.c +++ b/net/core/gen_estimator.c @@ -90,10 +90,12 @@ static void est_timer(struct timer_list *t) rate = (b_packets - est->last_packets) << (10 - est->intvl_log); rate = (rate >> est->ewma_log) - (est->avpps >> est->ewma_log);
+ preempt_disable_nested(); write_seqcount_begin(&est->seq); est->avbps += brate; est->avpps += rate; write_seqcount_end(&est->seq); + preempt_enable_nested();
est->last_bytes = b_bytes; est->last_packets = b_packets;