4.16-stable review patch. If anyone has any objections, please let me know.
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From: Alexandre Belloni alexandre.belloni@bootlin.com
[ Upstream commit 10d0c768cc6d581523d673b9d1b54213f8a5eb24 ]
The IRQ is requested before the struct rtc is allocated and registered, but this struct is used in the IRQ handler, leading to:
Unable to handle kernel NULL pointer dereference at virtual address 0000017c pgd = a38a2f9b [0000017c] *pgd=00000000 Internal error: Oops: 5 [#1] ARM Modules linked in: CPU: 0 PID: 613 Comm: irq/48-m41t80 Not tainted 4.16.0-rc1+ #42 Hardware name: Atmel SAMA5 PC is at mutex_lock+0x14/0x38 LR is at m41t80_handle_irq+0x1c/0x9c pc : [<c06e864c>] lr : [<c04b70f0>] psr: 20000013 sp : dec73f30 ip : 00000000 fp : dec56d98 r10: df437cf0 r9 : c0a03008 r8 : c0145ffc r7 : df5c4300 r6 : dec568d0 r5 : df593000 r4 : 0000017c r3 : df592800 r2 : 60000013 r1 : df593000 r0 : 0000017c Flags: nzCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment none Control: 10c53c7d Table: 20004059 DAC: 00000051 Process irq/48-m41t80 (pid: 613, stack limit = 0xb52d091e) Stack: (0xdec73f30 to 0xdec74000) 3f20: dec56840 df5c4300 00000001 df5c4300 3f40: c0145ffc c0146018 dec56840 ffffe000 00000001 c0146290 dec567c0 00000000 3f60: c0146084 ed7c9a62 c014615c dec56d80 dec567c0 00000000 dec72000 dec56840 3f80: c014615c c012ffc0 dec72000 dec567c0 c012fe80 00000000 00000000 00000000 3fa0: 00000000 00000000 00000000 c01010e8 00000000 00000000 00000000 00000000 3fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 3fe0: 00000000 00000000 00000000 00000000 00000013 00000000 29282726 2d2c2b2a [<c06e864c>] (mutex_lock) from [<c04b70f0>] (m41t80_handle_irq+0x1c/0x9c) [<c04b70f0>] (m41t80_handle_irq) from [<c0146018>] (irq_thread_fn+0x1c/0x54) [<c0146018>] (irq_thread_fn) from [<c0146290>] (irq_thread+0x134/0x1c0) [<c0146290>] (irq_thread) from [<c012ffc0>] (kthread+0x140/0x148) [<c012ffc0>] (kthread) from [<c01010e8>] (ret_from_fork+0x14/0x2c) Exception stack(0xdec73fb0 to 0xdec73ff8) 3fa0: 00000000 00000000 00000000 00000000 3fc0: 00000000 00000000 00000000 00000000 00000000 00000000 00000000 00000000 3fe0: 00000000 00000000 00000000 00000000 00000013 00000000 Code: e3c33d7f e3c3303f f5d0f000 e593300c (e1901f9f) ---[ end trace 22b027302eb7c604 ]--- genirq: exiting task "irq/48-m41t80" (613) is an active IRQ thread (irq 48)
Also, there is another possible race condition. The probe function is not allowed to fail after the RTC is registered 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* */
Switch to devm_rtc_allocate_device/rtc_register_device to allocate the rtc before requesting the IRQ and register it as late as possible.
Signed-off-by: Alexandre Belloni alexandre.belloni@bootlin.com
Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/rtc/rtc-m41t80.c | 18 +++++++++++------- 1 file changed, 11 insertions(+), 7 deletions(-)
--- a/drivers/rtc/rtc-m41t80.c +++ b/drivers/rtc/rtc-m41t80.c @@ -885,7 +885,6 @@ static int m41t80_probe(struct i2c_clien { struct i2c_adapter *adapter = to_i2c_adapter(client->dev.parent); int rc = 0; - struct rtc_device *rtc = NULL; struct rtc_time tm; struct m41t80_data *m41t80_data = NULL; bool wakeup_source = false; @@ -909,6 +908,10 @@ static int m41t80_probe(struct i2c_clien m41t80_data->features = id->driver_data; i2c_set_clientdata(client, m41t80_data);
+ m41t80_data->rtc = devm_rtc_allocate_device(&client->dev); + if (IS_ERR(m41t80_data->rtc)) + return PTR_ERR(m41t80_data->rtc); + #ifdef CONFIG_OF wakeup_source = of_property_read_bool(client->dev.of_node, "wakeup-source"); @@ -932,15 +935,11 @@ static int m41t80_probe(struct i2c_clien device_init_wakeup(&client->dev, true); }
- rtc = devm_rtc_device_register(&client->dev, client->name, - &m41t80_rtc_ops, THIS_MODULE); - if (IS_ERR(rtc)) - return PTR_ERR(rtc); + m41t80_data->rtc->ops = &m41t80_rtc_ops;
- m41t80_data->rtc = rtc; if (client->irq <= 0) { /* We cannot support UIE mode if we do not have an IRQ line */ - rtc->uie_unsupported = 1; + m41t80_data->rtc->uie_unsupported = 1; }
/* Make sure HT (Halt Update) bit is cleared */ @@ -993,6 +992,11 @@ static int m41t80_probe(struct i2c_clien if (m41t80_data->features & M41T80_FEATURE_SQ) m41t80_sqw_register_clk(m41t80_data); #endif + + rc = rtc_register_device(m41t80_data->rtc); + if (rc) + return rc; + return 0; }