From 44b8fb6eaa7c3fb770bf1e37619cdb3902cca1fc Mon Sep 17 00:00:00 2001 From: Madhuparna Bhowmik Date: Fri, 17 Apr 2020 21:04:51 +0530 Subject: [PATCH] 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: Madhuparna Bhowmik Link: https://lore.kernel.org/r/20200417153451.1551-1-madhuparnabhowmik10@gmail.com Signed-off-by: Greg Kroah-Hartman --- drivers/char/tlclk.c | 19 +++++++++++-------- 1 file changed, 11 insertions(+), 8 deletions(-) diff --git a/drivers/char/tlclk.c b/drivers/char/tlclk.c index 6d81bb3bb503..896a3550fba9 100644 --- a/drivers/char/tlclk.c +++ b/drivers/char/tlclk.c @@ -777,18 +777,22 @@ static int __init tlclk_init(void) { int ret; - ret = register_chrdev(tlclk_major, "telco_clock", &tlclk_fops); - if (ret < 0) { - printk(KERN_ERR "tlclk: can't get major %d.\n", tlclk_major); - return ret; - } - tlclk_major = 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); + if (ret < 0) { + printk(KERN_ERR "tlclk: can't get major %d.\n", tlclk_major); + kfree(alarm_events); + return ret; + } + tlclk_major = ret; + /* Read telecom clock IRQ number (Set by BIOS) */ if (!request_region(TLCLK_BASE, 8, "telco_clock")) { printk(KERN_ERR "tlclk: request_region 0x%X failed.\n", @@ -796,7 +800,6 @@ static int __init tlclk_init(void) ret = -EBUSY; goto out2; } - telclk_interrupt = (inb(TLCLK_REG7) & 0x0f); if (0x0F == telclk_interrupt ) { /* not MCPBL0010 ? */ printk(KERN_ERR "telclk_interrupt = 0x%x non-mcpbl0010 hw.\n", @@ -837,8 +840,8 @@ out3: release_region(TLCLK_BASE, 8); out2: kfree(alarm_events); -out1: unregister_chrdev(tlclk_major, "telco_clock"); +out1: return ret; }