From 994ec64c0a193940be7a6fd074668b9446d3b6c3 Mon Sep 17 00:00:00 2001 From: Alexandre Belloni Date: Mon, 4 Dec 2017 14:58:33 +0100 Subject: rtc: ac100: Fix multiple race conditions The probe function is not allowed to fail after registering the RTC because the following may happen: CPU0: CPU1: sys_load_module() do_init_module() do_one_initcall() cmos_do_probe() rtc_device_register() __register_chrdev() cdev->owner = struct module* open("/dev/rtc0") rtc_device_unregister() module_put() free_module() module_free(mod->module_core) /* struct module *module is now freed */ chrdev_open() spin_lock(cdev_lock) cdev_get() try_module_get() module_is_live() /* dereferences already freed struct module* */ Also, the interrupt handler: ac100_rtc_irq() is dereferencing chip->rtc but this may still be NULL when it is called, resulting in: Unable to handle kernel NULL pointer dereference at virtual address 00000194 pgd = (ptrval) [00000194] *pgd=00000000 Internal error: Oops: 5 [#1] SMP ARM Modules linked in: CPU: 0 PID: 72 Comm: irq/71-ac100-rt Not tainted 4.15.0-rc1-next-20171201-dirty #120 Hardware name: Allwinner sun8i Family task: (ptrval) task.stack: (ptrval) PC is at mutex_lock+0x14/0x3c LR is at ac100_rtc_irq+0x38/0xc8 pc : [] lr : [] psr: 60000053 sp : ee9c9f28 ip : 00000000 fp : ee9adfdc r10: 00000000 r9 : c0a04c48 r8 : c015ed18 r7 : ee9bd600 r6 : ee9c9f28 r5 : ee9af590 r4 : c0a04c48 r3 : ef3cb3c0 r2 : 00000000 r1 : ee9af590 r0 : 00000194 Flags: nZCv IRQs on FIQs off Mode SVC_32 ISA ARM Segment none Control: 10c5387d Table: 4000406a DAC: 00000051 Process irq/71-ac100-rt (pid: 72, stack limit = 0x(ptrval)) Stack: (0xee9c9f28 to 0xee9ca000) 9f20: 00000000 7c2fd1be c015ed18 ee9adf40 ee9c0400 ee9c0400 9f40: ee9adf40 c015ed34 ee9c8000 ee9adf64 ee9c0400 c015f040 ee9adf80 00000000 9f60: c015ee24 7c2fd1be ee9adfc0 ee9adf80 00000000 ee9c8000 ee9adf40 c015eef4 9f80: ef1eba34 c0138f14 ee9c8000 ee9adf80 c0138df4 00000000 00000000 00000000 9fa0: 00000000 00000000 00000000 c01010e8 00000000 00000000 00000000 00000000 9fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 9fe0: 00000000 00000000 00000000 00000000 00000013 00000000 ffffffff ffffffff [] (mutex_lock) from [] (ac100_rtc_irq+0x38/0xc8) [] (ac100_rtc_irq) from [] (irq_thread_fn+0x1c/0x54) [] (irq_thread_fn) from [] (irq_thread+0x14c/0x214) [] (irq_thread) from [] (kthread+0x120/0x150) [] (kthread) from [] (ret_from_fork+0x14/0x2c) Solve both issues by moving to devm_rtc_allocate_device()/rtc_register_device() Reported-by: Quentin Schulz Tested-by: Quentin Schulz Signed-off-by: Alexandre Belloni --- drivers/rtc/rtc-ac100.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) (limited to 'drivers/rtc/rtc-ac100.c') diff --git a/drivers/rtc/rtc-ac100.c b/drivers/rtc/rtc-ac100.c index 9e336184491c..0e358d4b6738 100644 --- a/drivers/rtc/rtc-ac100.c +++ b/drivers/rtc/rtc-ac100.c @@ -567,6 +567,12 @@ static int ac100_rtc_probe(struct platform_device *pdev) return chip->irq; } + chip->rtc = devm_rtc_allocate_device(&pdev->dev); + if (IS_ERR(chip->rtc)) + return PTR_ERR(chip->rtc); + + chip->rtc->ops = &ac100_rtc_ops; + ret = devm_request_threaded_irq(&pdev->dev, chip->irq, NULL, ac100_rtc_irq, IRQF_SHARED | IRQF_ONESHOT, @@ -586,17 +592,16 @@ static int ac100_rtc_probe(struct platform_device *pdev) /* clear counter alarm pending interrupts */ regmap_write(chip->regmap, AC100_ALM_INT_STA, AC100_ALM_INT_ENABLE); - chip->rtc = devm_rtc_device_register(&pdev->dev, "rtc-ac100", - &ac100_rtc_ops, THIS_MODULE); - if (IS_ERR(chip->rtc)) { - dev_err(&pdev->dev, "unable to register device\n"); - return PTR_ERR(chip->rtc); - } - ret = ac100_rtc_register_clks(chip); if (ret) return ret; + ret = rtc_register_device(chip->rtc); + if (ret) { + dev_err(&pdev->dev, "unable to register device\n"); + return ret; + } + dev_info(&pdev->dev, "RTC enabled\n"); return 0; -- cgit