From: Zhenzhong Duan <zhenzhong.duan@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: x86@kernel.org, Zhenzhong Duan <zhenzhong.duan@gmail.com>,
Arnd Bergmann <arnd@arndb.de>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: [PATCH RESEND] ttyprintk: fix a potential sleeping in interrupt context issue
Date: Fri, 3 Jan 2020 11:45:41 +0800 [thread overview]
Message-ID: <20200103034541.5302-1-zhenzhong.duan@gmail.com> (raw)
Google syzbot reports:
BUG: sleeping function called from invalid context at
kernel/locking/mutex.c:938
in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 0, name: swapper/1
1 lock held by swapper/1/0:
...
Call Trace:
<IRQ>
dump_stack+0x197/0x210
___might_sleep.cold+0x1fb/0x23e
__might_sleep+0x95/0x190
__mutex_lock+0xc5/0x13c0
mutex_lock_nested+0x16/0x20
tpk_write+0x5d/0x340
resync_tnc+0x1b6/0x320
call_timer_fn+0x1ac/0x780
run_timer_softirq+0x6c3/0x1790
__do_softirq+0x262/0x98c
irq_exit+0x19b/0x1e0
smp_apic_timer_interrupt+0x1a3/0x610
apic_timer_interrupt+0xf/0x20
</IRQ>
Fix it by using spinlock in process context instead of mutex and having
interrupt disabled in critical section.
Signed-off-by: Zhenzhong Duan <zhenzhong.duan@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/char/ttyprintk.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/drivers/char/ttyprintk.c b/drivers/char/ttyprintk.c
index 4f24e46ebe7c..56db949a7b70 100644
--- a/drivers/char/ttyprintk.c
+++ b/drivers/char/ttyprintk.c
@@ -15,10 +15,11 @@
#include <linux/serial.h>
#include <linux/tty.h>
#include <linux/module.h>
+#include <linux/spinlock.h>
struct ttyprintk_port {
struct tty_port port;
- struct mutex port_write_mutex;
+ spinlock_t spinlock;
};
static struct ttyprintk_port tpk_port;
@@ -99,11 +100,12 @@ static int tpk_open(struct tty_struct *tty, struct file *filp)
static void tpk_close(struct tty_struct *tty, struct file *filp)
{
struct ttyprintk_port *tpkp = tty->driver_data;
+ unsigned long flags;
- mutex_lock(&tpkp->port_write_mutex);
+ spin_lock_irqsave(&tpkp->spinlock, flags);
/* flush tpk_printk buffer */
tpk_printk(NULL, 0);
- mutex_unlock(&tpkp->port_write_mutex);
+ spin_unlock_irqrestore(&tpkp->spinlock, flags);
tty_port_close(&tpkp->port, tty, filp);
}
@@ -115,13 +117,14 @@ static int tpk_write(struct tty_struct *tty,
const unsigned char *buf, int count)
{
struct ttyprintk_port *tpkp = tty->driver_data;
+ unsigned long flags;
int ret;
/* exclusive use of tpk_printk within this tty */
- mutex_lock(&tpkp->port_write_mutex);
+ spin_lock_irqsave(&tpkp->spinlock, flags);
ret = tpk_printk(buf, count);
- mutex_unlock(&tpkp->port_write_mutex);
+ spin_unlock_irqrestore(&tpkp->spinlock, flags);
return ret;
}
@@ -171,7 +174,7 @@ static int __init ttyprintk_init(void)
{
int ret = -ENOMEM;
- mutex_init(&tpk_port.port_write_mutex);
+ spin_lock_init(&tpk_port.spinlock);
ttyprintk_driver = tty_alloc_driver(1,
TTY_DRIVER_RESET_TERMIOS |
--
2.17.1
next reply other threads:[~2020-01-03 3:46 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-03 3:45 Zhenzhong Duan [this message]
2020-01-03 8:43 ` [PATCH RESEND] ttyprintk: fix a potential sleeping in interrupt context issue Greg Kroah-Hartman
2020-01-06 2:44 ` Zhenzhong Duan
2020-01-11 19:47 ` Greg Kroah-Hartman
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