Re: [PATCH 1/2] net: phy: leds: Clear phy_num_led_triggers on failure to avoid crash

From: Florian Fainelli
Date: Tue Jan 24 2017 - 15:52:23 EST

On 01/24/2017 07:41 AM, Geert Uytterhoeven wrote:
> phy_attach_direct() ignores errors returned by
> phy_led_triggers_register(). I think that's OK, as LED triggers can be
> considered a non-critical feature.
> However, this causes problems later:
> - phy_led_trigger_change_speed() will access the array
> phy_device.phy_led_triggers, which has been freed in the error path
> of phy_led_triggers_register(), which may lead to a crash.
> - phy_led_triggers_unregister() will access the same array, leading to
> crashes during s2ram or poweroff, like:
> Unable to handle kernel NULL pointer dereference at virtual address
> 00000000
> ...
> [<c04116d4>] (__list_del_entry_valid) from [<c05e8948>] (led_trigger_unregister+0x34/0xcc)
> [<c05e8948>] (led_trigger_unregister) from [<c05336c4>] (phy_led_triggers_unregister+0x28/0x34)
> [<c05336c4>] (phy_led_triggers_unregister) from [<c0531d44>] (phy_detach+0x30/0x74)
> [<c0531d44>] (phy_detach) from [<c0538bdc>] (sh_eth_close+0x64/0x9c)
> [<c0538bdc>] (sh_eth_close) from [<c04d4ce0>] (dpm_run_callback+0x48/0xc8)
> or:
> list_del corruption. prev->next should be dede6540, but was 2e323931
> ------------[ cut here ]------------
> kernel BUG at lib/list_debug.c:52!
> ...
> [<c02f6d70>] (__list_del_entry_valid) from [<c0425168>] (led_trigger_unregister+0x34/0xcc)
> [<c0425168>] (led_trigger_unregister) from [<c03a05a0>] (phy_led_triggers_unregister+0x28/0x34)
> [<c03a05a0>] (phy_led_triggers_unregister) from [<c039ec04>] (phy_detach+0x30/0x74)
> [<c039ec04>] (phy_detach) from [<c03a4fc0>] (sh_eth_close+0x6c/0xa4)
> [<c03a4fc0>] (sh_eth_close) from [<c0483234>] (__dev_close_many+0xac/0xd0)
> To fix this, clear phy_device.phy_num_led_triggers in the error path of
> phy_led_triggers_register() fails.
> Note that the "No phy led trigger registered for speed" message will
> still be printed on link speed changes, which is a good cue that
> something went wrong with the LED triggers.
> Fixes: 2e0bc452f4721520 ("net: phy: leds: add support for led triggers on phy link state change")
> Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>

Reviewed-by: Florian Fainelli <f.fainelli@xxxxxxxxx>