Commit 1510dd59 authored Oct 31, 2011 by Éric Piel Committed by Linus Torvalds Oct 31, 2011

lis3lv02d: avoid divide by zero due to unchecked



After an "unexpected" reboot, I found this Oops in my logs:

divide error: 0000 [#1] PREEMPT SMP=20
CPU 0=20
Modules linked in: lis3lv02d hp_wmi input_polldev [...]
Pid: 390, comm: modprobe Tainted: G         C  2.6.39-rc7-wl+=20
RIP: 0010:[<ffffffffa014b427>]  [<ffffffffa014b427>]
		 lis3lv02d_poweron+0x4e/0x94 [lis3lv02d]
RSP: 0018:ffff8801d6407cf8  EFLAGS: 00010246
RAX: 0000000000000bb8 RBX: ffffffffa014e000 RCX: 0000000000000000
RDX: 0000000000000000 RSI: ffffea00066e4708 RDI: ffff8801df002700
RBP: ffff8801d6407d18 R08: ffffea00066c5a30 R09: ffffffff812498c9
R10: ffff8801d7bfcea0 R11: ffff8801d7bfce10 R12: 0000000000000bb8
R13: 00000000ffffffda R14: ffffffffa0154120 R15: ffffffffa0154030
=46S:  00007fc0705db700(0000) GS:ffff8801dfa00000(0000) knlGS:0
CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
CR2: 00007f33549174f0 CR3: 00000001d65c9000 CR4: 00000000000406f0
Process modprobe (pid: 390, threadinfo ffff8801d6406000, task ffff8801d6b40=
000)
Stack:
 ffffffffa0154120 62ffffffa0154030 ffffffffa014e000 00000000ffffffea
 ffff8801d6407d58 ffffffffa014bcc1 0000000000000000 0000000000000048
 ffff8801d8bae800 00000000ffffffea 00000000ffffffda ffffffffa0154120
Call Trace:
 [<ffffffffa014bcc1>] lis3lv02d_init_device+0x1ce/0x496 [lis3lv02d]
 [<ffffffffa01522ff>] lis3lv02d_add+0x10f/0x17c [hp_accel]
 [<ffffffff81233e11>] acpi_device_probe+0x49/0x117
[...]
Code: 3a 75 06 80 4d ef 50 eb 04 80 4d ef 40 0f b6 55 ef be 21
00 00 00 48 89 df ff 53 18 44 8b 63 6c e8 3e fc ff ff 89 c1 44
89 e0 99 <f7> f9 89 c7 e8 93 82 ef e0 48 83 7b 30 00 74 2d 45
31 e4 80 7b=20
RIP  [<ffffffffa014b427>] lis3lv02d_poweron+0x4e/0x94 [lis3lv02d]
 RSP <ffff8801d6407cf8>

>From my POV, it looks like the hardware is not working as expected
and returns a bogus data rate. The driver doesn't check the result
and directly uses it as some sort of divisor in some places:

msleep(lis3->pwron_delay / lis3lv02d_get_odr());

Under this circumstances, this could very well cause the
"divide by zero" exception from above.

For now, I fixed it the easiest and most obvious way:
Check if the result is sane and if it isn't use a sane default
instead. I went for "100" in the latter case, simply because
/sys/devices/platform/lis3lv02d/rate returns it on a successful
boot.

Signed-off-by: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: Éric Piel <eric.piel@tremplin-utc.net>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Witold Pilat <witold.pilat@gmail.com>
Cc: Lyall Pearce <lyall.pearce@hp.com>
Cc: Malte Starostik <m-starostik@versanet.de>
Cc: Ilkka Koskinen <ilkka.koskinen@nokia.com>
Cc: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Cc: Christian Lamparter <chunkeey@googlemail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 65807044

drivers/misc/lis3lv02d/lis3lv02d.c

+30 −6

Original line number	Diff line number	Diff line
		@@ -206,6 +206,18 @@ static int lis3lv02d_get_odr(void)
		return lis3_dev.odrs[(ctrl >> shift)];
		}

		static int lis3lv02d_get_pwron_wait(struct lis3lv02d *lis3)
		{
		int div = lis3lv02d_get_odr();

		if (WARN_ONCE(div == 0, "device returned spurious data"))
		return -ENXIO;

		/* LIS3 power on delay is quite long */
		msleep(lis3->pwron_delay / div);
		return 0;
		}

		static int lis3lv02d_set_odr(int rate)
		{
		u8 ctrl;
		@@ -266,7 +278,9 @@ static int lis3lv02d_selftest(struct lis3lv02d *lis3, s16 results[3])

		lis3->read(lis3, ctlreg, &reg);
		lis3->write(lis3, ctlreg, (reg \| selftest));
		msleep(lis3->pwron_delay / lis3lv02d_get_odr());
		ret = lis3lv02d_get_pwron_wait(lis3);
		if (ret)
		goto fail;

		/* Read directly to avoid axis remap */
		x = lis3->read_data(lis3, OUTX);
		@@ -275,7 +289,9 @@ static int lis3lv02d_selftest(struct lis3lv02d *lis3, s16 results[3])

		/* back to normal settings */
		lis3->write(lis3, ctlreg, reg);
		msleep(lis3->pwron_delay / lis3lv02d_get_odr());
		ret = lis3lv02d_get_pwron_wait(lis3);
		if (ret)
		goto fail;

		results[0] = x - lis3->read_data(lis3, OUTX);
		results[1] = y - lis3->read_data(lis3, OUTY);
		@@ -363,8 +379,9 @@ void lis3lv02d_poweroff(struct lis3lv02d *lis3)
		}
		EXPORT_SYMBOL_GPL(lis3lv02d_poweroff);

		void lis3lv02d_poweron(struct lis3lv02d *lis3)
		int lis3lv02d_poweron(struct lis3lv02d *lis3)
		{
		int err;
		u8 reg;

		lis3->init(lis3);
		@@ -384,11 +401,14 @@ void lis3lv02d_poweron(struct lis3lv02d *lis3)
		lis3->write(lis3, CTRL_REG2, reg);
		}

		/* LIS3 power on delay is quite long */
		msleep(lis3->pwron_delay / lis3lv02d_get_odr());
		err = lis3lv02d_get_pwron_wait(lis3);
		if (err)
		return err;

		if (lis3->reg_ctrl)
		lis3_context_restore(lis3);

		return 0;
		}
		EXPORT_SYMBOL_GPL(lis3lv02d_poweron);

		@@ -928,7 +948,11 @@ int lis3lv02d_init_device(struct lis3lv02d *dev)
		atomic_set(&dev->wake_thread, 0);

		lis3lv02d_add_fs(dev);
		lis3lv02d_poweron(dev);
		err = lis3lv02d_poweron(dev);
		if (err) {
		lis3lv02d_remove_fs(dev);
		return err;
		}

		if (dev->pm_dev) {
		pm_runtime_set_active(dev->pm_dev);

drivers/misc/lis3lv02d/lis3lv02d.h

+1 −1

Original line number	Diff line number	Diff line
		@@ -285,7 +285,7 @@ int lis3lv02d_init_device(struct lis3lv02d *lis3);
		int lis3lv02d_joystick_enable(void);
		void lis3lv02d_joystick_disable(void);
		void lis3lv02d_poweroff(struct lis3lv02d *lis3);
		void lis3lv02d_poweron(struct lis3lv02d *lis3);
		int lis3lv02d_poweron(struct lis3lv02d *lis3);
		int lis3lv02d_remove_fs(struct lis3lv02d *lis3);

		extern struct lis3lv02d lis3_dev;

drivers/platform/x86/hp_accel.c

+1 −2

Original line number	Diff line number	Diff line
		@@ -354,8 +354,7 @@ static int lis3lv02d_suspend(struct acpi_device *device, pm_message_t state)

		static int lis3lv02d_resume(struct acpi_device *device)
		{
		lis3lv02d_poweron(&lis3_dev);
		return 0;
		return lis3lv02d_poweron(&lis3_dev);
		}
		#else
		#define lis3lv02d_suspend NULL