Re: [PATCH v6 13/22] ACPI: Change power supply ownership from driver to core

Rafael J. Wysocki
2015-03-10T19:29:07Z

On Tuesday, March 10, 2015 03:17:59 PM Sebastian Reichel wrote:
>
> --P+33d92oIH25kiaB
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>
> Hi Rafael and Len,
>
> On Tue, Mar 10, 2015 at 09:27:17AM +0100, Krzysztof Kozlowski wrote:
> > Change the ownership of power_supply structure from each driver
> > implementing the class to the power supply core.
> >=20
> > The patch changes power_supply_register() function thus all drivers
> > implementing power supply class are adjusted.
> >=20
> > Each driver provides the implementation of power supply. However it
> > should not be the owner of power supply class instance because it is
> > exposed by core to other subsystems with power_supply_get_by_name().
> > These other subsystems have no knowledge when the driver will unregister
> > the power supply. This leads to several issues when driver is unbound -
> > mostly because user of power supply accesses freed memory.
> >=20
> > Instead let the core own the instance of struct 'power_supply'. Other
> > users of this power supply will still access valid memory because it
> > will be freed when device reference count reaches 0. Currently this
> > means "it will leak" but power_supply_put() call in next patches will
> > solve it.
> >=20
> > This solves invalid memory references in following race condition
> > scenario:
> >=20
> > Thread 1: charger manager
> > Thread 2: power supply driver, used by charger manager
> >=20
> > THREAD 1 (charger manager) THREAD 2 (power supply driver)
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
> =3D=3D =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
> =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > psy =3D power_supply_get_by_name()
> > Driver unbind, .remove
> > power_supply_unregister()
> > Device fully removed
> > psy->get_property()
> >=20
> > The 'get_property' call is executed in invalid context because the driver=
> was
> > unbound and struct 'power_supply' memory was freed.
> >=20
> > This could be observed easily with charger manager driver (here compiled
> > with max17040 fuel gauge):
> >=20
> > $ cat /sys/devices/virtual/power_supply/cm-battery/capacity &
> > $ echo "1-0036" > /sys/bus/i2c/drivers/max17040/unbind
> > [ 55.725123] Unable to handle kernel NULL pointer dereference at virtua=
> l address 00000000
> > [ 55.732584] pgd =3D d98d4000
> > [ 55.734060] [00000000] *pgd=3D5afa2831, *pte=3D00000000, *ppte=3D00000=
> 000
> > [ 55.740318] Internal error: Oops: 80000007 [#1] PREEMPT SMP ARM
> > [ 55.746210] Modules linked in:
> > [ 55.749259] CPU: 1 PID: 2936 Comm: cat Tainted: G W 3.19.=
> 0-rc1-next-20141226-00048-gf79f475f3c44-dirty #1496
> > [ 55.760190] Hardware name: SAMSUNG EXYNOS (Flattened Device Tree)
> > [ 55.766270] task: d9b76f00 ti: daf54000 task.ti: daf54000
> > [ 55.771647] PC is at 0x0
> > [ 55.774182] LR is at charger_get_property+0x2f4/0x36c
> > [ 55.779201] pc : [<00000000>] lr : [<c034b0b4>] psr: 60000013
> > [ 55.779201] sp : daf55e90 ip : 00000003 fp : 00000000
> > [ 55.790657] r10: 00000000 r9 : c06e2878 r8 : d9b26c68
> > [ 55.795865] r7 : dad81610 r6 : daec7410 r5 : daf55ebc r4 : 00000000
> > [ 55.802367] r3 : 00000000 r2 : daf55ebc r1 : 0000002a r0 : d9b26c68
> > [ 55.808879] Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segme=
> nt user
> > [ 55.815994] Control: 10c5387d Table: 598d406a DAC: 00000015
> > [ 55.821723] Process cat (pid: 2936, stack limit =3D 0xdaf54210)
> > [ 55.827451] Stack: (0xdaf55e90 to 0xdaf56000)
> > [ 55.831795] 5e80: 60000013 c01459c=
> 4 0000002a c06f8ef8
> > [ 55.839956] 5ea0: db651000 c06f8ef8 daebac00 c04cb668 daebac08 c034686=
> 4 00000000 c01459c4
> > [ 55.848115] 5ec0: d99eaa80 c06f8ef8 00000fff 00001000 db651000 c027f25=
> c c027f240 d99eaa80
> > [ 55.856274] 5ee0: d9a06c00 c0146218 daf55f18 00001000 d99eaa80 db4c18c=
> 0 00000001 00000001
> > [ 55.864468] 5f00: daf55f80 c0144c78 c0144c54 c0107f90 00015000 d99eaab=
> 0 00000000 00000000
> > [ 55.872603] 5f20: 000051c7 00000000 db4c18c0 c04a9370 00015000 0000100=
> 0 daf55f80 00001000
> > [ 55.880763] 5f40: daf54000 00015000 00000000 c00e53dc db4c18c0 c00e548=
> c 0000000d 00008124
> > [ 55.888937] 5f60: 00000001 00000000 00000000 db4c18c0 db4c18c0 0000100=
> 0 00015000 c00e5550
> > [ 55.897099] 5f80: 00000000 00000000 00001000 00001000 00015000 0000000=
> 3 00000003 c000f364
> > [ 55.905239] 5fa0: 00000000 c000f1a0 00001000 00015000 00000003 0001500=
> 0 00001000 0001333c
> > [ 55.913399] 5fc0: 00001000 00015000 00000003 00000003 00000002 0000000=
> 0 00000000 00000000
> > [ 55.921560] 5fe0: 7fffe000 be999850 0000a225 b6f3c19c 60000010 0000000=
> 3 00000000 00000000
> > [ 55.929744] [<c034b0b4>] (charger_get_property) from [<c0346864>] (pow=
> er_supply_show_property+0x48/0x20c)
> > [ 55.939286] [<c0346864>] (power_supply_show_property) from [<c027f25c>=
> ] (dev_attr_show+0x1c/0x48)
> > [ 55.948130] [<c027f25c>] (dev_attr_show) from [<c0146218>] (sysfs_kf_s=
> eq_show+0x84/0x104)
> > [ 55.956298] [<c0146218>] (sysfs_kf_seq_show) from [<c0144c78>] (kernfs=
> _seq_show+0x24/0x28)
> > [ 55.964536] [<c0144c78>] (kernfs_seq_show) from [<c0107f90>] (seq_read=
> +0x1b0/0x484)
> > [ 55.972172] [<c0107f90>] (seq_read) from [<c00e53dc>] (__vfs_read+0x18=
> /0x4c)
> > [ 55.979188] [<c00e53dc>] (__vfs_read) from [<c00e548c>] (vfs_read+0x7c=
> /0x100)
> > [ 55.986304] [<c00e548c>] (vfs_read) from [<c00e5550>] (SyS_read+0x40/0=
> x8c)
> > [ 55.993164] [<c00e5550>] (SyS_read) from [<c000f1a0>] (ret_fast_syscal=
> l+0x0/0x48)
> > [ 56.000626] Code: bad PC value
> > [ 56.011652] ---[ end trace 7b64343fbdae8ef1 ]---
> >=20
> > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
> > Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>
> >=20
> > [for the nvec part]
> > Reviewed-by: Marc Dietrich <marvin24@gmx.de>
> >=20
> > [for compal-laptop.c]
> > Acked-by: Darren Hart <dvhart@linux.intel.com>
> >=20
> > [for the mfd part]
> > Acked-by: Lee Jones <lee.jones@linaro.org>
> > ---
> > [...]
> > drivers/acpi/ac.c | 32 ++--
> > drivers/acpi/battery.c | 55 ++++---
> > drivers/acpi/sbs.c | 68 +++++----
> > [...]
> > 82 files changed, 2296 insertions(+), 1839 deletions(-)
>
> I would like to merge this patch via power-supply tree. Can you
> please provide your Acked-By?

I need more time to review this, sorry.

Also this patch was killed by spam filters on vger and in GMail, so I suppose
some people who need to see it are not able to.

Rafael