On Thu, 12 Mar 2015, Krzysztof Kozlowski wrote: > Change the ownership of power_supply structure from each driver > implementing the class to the power supply core. > > The patch changes power_supply_register() function thus all drivers > implementing power supply class are adjusted. > > 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. > > 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. > > This solves invalid memory references in following race condition > scenario: > > Thread 1: charger manager > Thread 2: power supply driver, used by charger manager > > THREAD 1 (charger manager) THREAD 2 (power supply driver) > ========================== ============================== > psy = power_supply_get_by_name() > Driver unbind, .remove > power_supply_unregister() > Device fully removed > psy->get_property() > > The 'get_property' call is executed in invalid context because the driver was > unbound and struct 'power_supply' memory was freed. > > This could be observed easily with charger manager driver (here compiled > with max17040 fuel gauge): > > $ 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 virtual address 00000000 > [ 55.732584] pgd = d98d4000 > [ 55.734060] [00000000] *pgd=5afa2831, *pte=00000000, *ppte=00000000 > [ 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 Segment user > [ 55.815994] Control: 10c5387d Table: 598d406a DAC: 00000015 > [ 55.821723] Process cat (pid: 2936, stack limit = 0xdaf54210) > [ 55.827451] Stack: (0xdaf55e90 to 0xdaf56000) > [ 55.831795] 5e80: 60000013 c01459c4 0000002a c06f8ef8 > [ 55.839956] 5ea0: db651000 c06f8ef8 daebac00 c04cb668 daebac08 c0346864 00000000 c01459c4 > [ 55.848115] 5ec0: d99eaa80 c06f8ef8 00000fff 00001000 db651000 c027f25c c027f240 d99eaa80 > [ 55.856274] 5ee0: d9a06c00 c0146218 daf55f18 00001000 d99eaa80 db4c18c0 00000001 00000001 > [ 55.864468] 5f00: daf55f80 c0144c78 c0144c54 c0107f90 00015000 d99eaab0 00000000 00000000 > [ 55.872603] 5f20: 000051c7 00000000 db4c18c0 c04a9370 00015000 00001000 daf55f80 00001000 > [ 55.880763] 5f40: daf54000 00015000 00000000 c00e53dc db4c18c0 c00e548c 0000000d 00008124 > [ 55.888937] 5f60: 00000001 00000000 00000000 db4c18c0 db4c18c0 00001000 00015000 c00e5550 > [ 55.897099] 5f80: 00000000 00000000 00001000 00001000 00015000 00000003 00000003 c000f364 > [ 55.905239] 5fa0: 00000000 c000f1a0 00001000 00015000 00000003 00015000 00001000 0001333c > [ 55.913399] 5fc0: 00001000 00015000 00000003 00000003 00000002 00000000 00000000 00000000 > [ 55.921560] 5fe0: 7fffe000 be999850 0000a225 b6f3c19c 60000010 00000003 00000000 00000000 > [ 55.929744] [<c034b0b4>] (charger_get_property) from [<c0346864>] (power_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_seq_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+0x40/0x8c) > [ 55.993164] [<c00e5550>] (SyS_read) from [<c000f1a0>] (ret_fast_syscall+0x0/0x48) > [ 56.000626] Code: bad PC value > [ 56.011652] ---[ end trace 7b64343fbdae8ef1 ]--- > > Signed-off-by: Krzysztof Kozlowski <k.kozlowski@xxxxxxxxxxx> > Reviewed-by: Bartlomiej Zolnierkiewicz <b.zolnierkie@xxxxxxxxxxx> > > [for the nvec part] > Reviewed-by: Marc Dietrich <marvin24@xxxxxx> > > [for compal-laptop.c] > Acked-by: Darren Hart <dvhart@xxxxxxxxxxxxxxx> > > [for the mfd part] > Acked-by: Lee Jones <lee.jones@xxxxxxxxxx> Acked-by: Jiri Kosina <jkosina@xxxxxxx> for drivers/hid/* -- Jiri Kosina SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-input" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
