netdev - [PATCH AUTOSEL 5.10 016/137] net: Treat __napi_schedule_irqoff() as __napi_schedule() on PREEMPT

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <20210706112203.2062605-16-sashal@kernel.org>
Date:   Tue,  6 Jul 2021 07:20:02 -0400
From:   Sasha Levin <sashal@...nel.org>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:     Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Juri Lelli <juri.lelli@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "David S . Miller" <davem@...emloft.net>,
        Sasha Levin <sashal@...nel.org>, netdev@...r.kernel.org
Subject: [PATCH AUTOSEL 5.10 016/137] net: Treat __napi_schedule_irqoff() as __napi_schedule() on PREEMPT_RT

From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>

[ Upstream commit 8380c81d5c4fced6f4397795a5ae65758272bbfd ]

__napi_schedule_irqoff() is an optimized version of __napi_schedule()
which can be used where it is known that interrupts are disabled,
e.g. in interrupt-handlers, spin_lock_irq() sections or hrtimer
callbacks.

On PREEMPT_RT enabled kernels this assumptions is not true. Force-
threaded interrupt handlers and spinlocks are not disabling interrupts
and the NAPI hrtimer callback is forced into softirq context which runs
with interrupts enabled as well.

Chasing all usage sites of __napi_schedule_irqoff() is a whack-a-mole
game so make __napi_schedule_irqoff() invoke __napi_schedule() for
PREEMPT_RT kernels.

The callers of ____napi_schedule() in the networking core have been
audited and are correct on PREEMPT_RT kernels as well.

Reported-by: Juri Lelli <juri.lelli@...hat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Reviewed-by: Thomas Gleixner <tglx@...utronix.de>
Reviewed-by: Juri Lelli <juri.lelli@...hat.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 net/core/dev.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 0c9ce36afc8c..2fdf30eefc59 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6433,11 +6433,18 @@ EXPORT_SYMBOL(napi_schedule_prep);
  * __napi_schedule_irqoff - schedule for receive
  * @n: entry to schedule
  *
- * Variant of __napi_schedule() assuming hard irqs are masked
+ * Variant of __napi_schedule() assuming hard irqs are masked.
+ *
+ * On PREEMPT_RT enabled kernels this maps to __napi_schedule()
+ * because the interrupt disabled assumption might not be true
+ * due to force-threaded interrupts and spinlock substitution.
  */
 void __napi_schedule_irqoff(struct napi_struct *n)
 {
-	____napi_schedule(this_cpu_ptr(&softnet_data), n);
+	if (!IS_ENABLED(CONFIG_PREEMPT_RT))
+		____napi_schedule(this_cpu_ptr(&softnet_data), n);
+	else
+		__napi_schedule(n);
 }
 EXPORT_SYMBOL(__napi_schedule_irqoff);
 
-- 
2.30.2