Commit 44b8fb6e authored by Madhuparna Bhowmik's avatar Madhuparna Bhowmik Committed by Greg Kroah-Hartman
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drivers: char: tlclk.c: Avoid data race between init and interrupt handler 



After registering character device the file operation callbacks can be
called. The open callback registers interrupt handler.
Therefore interrupt handler can execute in parallel with rest of the init
function. To avoid such data race initialize telclk_interrupt variable
and struct alarm_events before registering character device.

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: default avatarMadhuparna Bhowmik <madhuparnabhowmik10@gmail.com>
Link: https://lore.kernel.org/r/20200417153451.1551-1-madhuparnabhowmik10@gmail.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent c18c1f10

drivers/char/tlclk.c

+10 −7
Original line number Original line Diff line number Diff line
@@ -777,17 +777,21 @@ static int __init tlclk_init(void) 
{

{

	int ret;

	int ret;





	telclk_interrupt = (inb(TLCLK_REG7) & 0x0f);



	alarm_events = kzalloc( sizeof(struct tlclk_alarms), GFP_KERNEL);

	if (!alarm_events) {

		ret = -ENOMEM;

		goto out1;

	}



	ret = register_chrdev(tlclk_major, "telco_clock", &tlclk_fops);

	ret = register_chrdev(tlclk_major, "telco_clock", &tlclk_fops);

	if (ret < 0) {

	if (ret < 0) {

		printk(KERN_ERR "tlclk: can't get major %d.\n", tlclk_major);

		printk(KERN_ERR "tlclk: can't get major %d.\n", tlclk_major);

		kfree(alarm_events);

		return ret;

		return ret;

	}

	}

	tlclk_major = ret;

	tlclk_major = ret;

	alarm_events = kzalloc( sizeof(struct tlclk_alarms), GFP_KERNEL);

	if (!alarm_events) {

		ret = -ENOMEM;

		goto out1;

	}





	/* Read telecom clock IRQ number (Set by BIOS) */

	/* Read telecom clock IRQ number (Set by BIOS) */

	if (!request_region(TLCLK_BASE, 8, "telco_clock")) {

	if (!request_region(TLCLK_BASE, 8, "telco_clock")) {
@@ -796,7 +800,6 @@ static int __init tlclk_init(void) 
		ret = -EBUSY;

		ret = -EBUSY;

		goto out2;

		goto out2;

	}

	}

	telclk_interrupt = (inb(TLCLK_REG7) & 0x0f);





	if (0x0F == telclk_interrupt ) { /* not MCPBL0010 ? */

	if (0x0F == telclk_interrupt ) { /* not MCPBL0010 ? */

		printk(KERN_ERR "telclk_interrupt = 0x%x non-mcpbl0010 hw.\n",

		printk(KERN_ERR "telclk_interrupt = 0x%x non-mcpbl0010 hw.\n",
@@ -837,8 +840,8 @@ static int __init tlclk_init(void) 
	release_region(TLCLK_BASE, 8);

	release_region(TLCLK_BASE, 8);

out2:

out2:

	kfree(alarm_events);

	kfree(alarm_events);

out1:

	unregister_chrdev(tlclk_major, "telco_clock");

	unregister_chrdev(tlclk_major, "telco_clock");

out1:

	return ret;

	return ret;

}

}